Electric double-layer capacitor and method for manufacturing the same

ABSTRACT

The invention relates to an electric double layer capacitor for large capacity used in regeneration or electric power storage for various electric appliances and electric vehicles, and its manufacturing method. As the resin to be used in the current collector, by adding low softening point resin, polytetrafluoroethylene resin, latex resin or the like, the flexibility, thick coating performance and winding performance are improved. By preparing the electrode solution for making such current collector by using a high pressure dispersion machine, the capacity and density of the current collector can be enhanced substantially. According to this manufacturing method, the electric double layer capacitor may be further increased in size, increased in capacity and lowered in cost.

This application is a 371 of PCT/JP98/02603 filed Jun. 12, 1998.

TECHNICAL FIELD

The present invention relates to an electric double layer capacitor forlarge capacity used for regeneration or electric power storage forvarious electric appliances and electric vehicles, and its manufacturingmethod.

BACKGROUND ART

An electric double layer capacitor is constituted by winding orlaminating a plurality of conductive foils of aluminum or the likeforming a current collector on a separator, and sealing in a casetogether with a nonaqueous electrolyte solution. This electric doublelayer capacitor is, recently, expanding its applications in regenerationor electric power storage for various electric appliances and electricvehicles. Accordingly, the electric double layer capacitor is furtherdemanded to be higher in performance, larger in capacity, superior inreliability, and lower in cost.

In the hitherto proposed electric double layer capacitor, as disclosedin Japanese Laid-open Patent No. 1-164017, a binder such aspolytetrafluoroethylene (PTFE) is kneaded with activated carbon orcarbon to form a current collector. It is, however, difficult todisperse fluorine derivative binder material uniformly in the currentcollector, and it was another problem to use an exclusive solvent. Tosolve these problems, in Japanese Laid-open Patent No. 6-316784, the useof ultrasonic homogenizer is proposed as a manufacturing technique ofuniform mixed powder of carbon black and PTFE, while Japanese Laid-openPatent No. 6-203849 and Japanese Laid-open Patent No. 8-203536 proposethe use of ultrasonic homogenizer as a technique for dispersing catalystand nickel together with carbon black in the fuel electrode of fuelcell, its catalyst manufacturing method, and battery operating method.In such methods, however, there was a limit in enhancement ofdispersion.

Incidentally, Japanese Laid-open Patent No. 63-104316 proposes the useof elastomer of which glass transition temperature is −10 deg. C. orless as the current collector. As examples of the elastomer, binders areproposed such as NBR, SBR, fluororubber, and silicone rubber. Alsoproposed is a method of dissolving such binder in an organic solvent,mixing Ketienblack therein to disperse the two, evaporating the solvent,and forming by blending with a roll. It is further proposed to wind anelastomer around a roll, add Ketienblack, mix, blend, and formsimultaneously. Such techniques are same as the conventional methodsused in manufacture of tires and other rubber kneaded products, and itis difficult to manufacture current collectors of high capacity such aslithium secondary battery and lead secondary battery by such methods. Asa similar example, Japanese Laid-open Patent No. 7-331201 proposes toknead rubber material as a binder of expanded graphite. In this case,the rubber material is dissolved in a solvent such as toluene, andcarbon powder is added and kneaded, and heated. In a method proposed inJapanese Laid-open Patent No. 8-250380, meanwhile, powder ofacrylonitrile-butadiene rubber is dissolved in a solvent such as xylene,and mixed with activated carbon powder and acetylene black, and finallythe solvent is evaporated, and the obtained mixture is formed in athickness of 50 to 500 microns by pressure forming method or by usingextrusion forming die. In such conventional dissolving methods, sincethe rubber material is completely dissolved (in other words, dissolvedor dispersed to a molecular state of several angstroms), and also poresfor forming the electric double layer of several angstroms on thesurface of activated carbon are clogged, it was a problem that theproduct capacity was lowered significantly. To solve such conventionalproblems, methods of kneading rubber and activated carbon or forming thecurrent collector have been proposed, but there were limits.

Meanwhile, as proposed in Japanese Laid-open Patent No. 62-16506 orJapanese Laid-open Patent No. 62-179711, activated carbon powder isdispersed in latex using water as dispersant, the mixed solution isdehydrated to remove solvent such as dispersant, the selected aggregatedmatter is dried, this aggregated matter is crushed, granulated, andfinally pressurized, and a disk-shaped current collector of 16 mm indiameter and 0.9 mm in thickness is formed. In this case, however, ittakes cost in drying and crushing.

On the other hand, as proposed in Japanese Laid-open Patent No.3-280518, ammonium salt of carboxyethyl cellulose or the like isdissolved in water, and activated carbon is mixed and dispersed, and theprepared solution is applied on an aluminum base material by a techniquesuch as roll coating or doctor blade coating to manufacture an electricdouble layer capacitor. Besides, Japanese Laid-open Patent No. 57-60828proposes to enhance the coat film density by a press, but since thecurrent collector is stiff and brittle, the coat film density is notenhanced unless pressed at a high pressure. When pressed at a highpressure, however, the electrode coat film may be broken, or may bepeeled off from the conductive foil, and further the conductiveelectrode may be elongated or deformed like seaweed. In this case, bydecreasing the resin amount, the pressing pressure may be somewhatlowered, but since the resin amount is small, the binding density of thecurrent collector coat film is insufficient (for example, the adhesionstrength of the conductive foil and activated carbon coat film isinsufficient, and aggregation breakage occurs in the activated carboncoat film itself). Therefore, it was a problem that the currentcollector was broken or peeled off when winding or laminating.

DISCLOSURE OF THE INVENTION

The invention is to solve such problems of the prior arts, and presentsan electric double layer capacitor capable of further increasing thecapacity, increasing the size, reducing the thickness, and lowering thecost, and its manufacturing method.

To achieve the object, in the electric double layer capacitor and itsmanufacturing method of the invention,

a current collector formed by dispersing activated carbon, conductiveagent, ethylene tetrafluoride resin, and at least one kind selected fromthe group consisting of ammonium salt of carboxy methyl cellulose resin,polyvinyl alcohol, methyl cellulose and hydroxy propyl cellulose resinis formed at least on one flat surface of the conductive film at adensity of 0.35 g/cc or more to 1.50 g/cc or less, and

a plurality of the conductive foils are wound or laminated on aseparator, and sealed in a nonaqueous electrolyte solution together withlead-out electrodes.

In this constitution, as compared with the conventional electric doublelayer capacitor of- coil type or the like with the height of severalcentimeters or less, by using such new current collector, it is possibleto further increase in size, increase in capacity, and decrease in cost.

Also according to the manufacturing method, the current collector itselfmay be applicable to flexibility, filling density, binding force,winding performance, and thick coating, and also reduction of equivalentseries resistance and reduction of impedance. As a result, theperformance of the electric double layer capacitor using this currentcollector may be further enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a winding type electric double layercapacitor in an embodiment of the invention, FIG. 2 is a perspectiveview for explaining a mode of evaluation of winding performance ofcurrent collector and conductive foil, FIG. 3 is a block diagram oflaminate type electric double layer capacitor, FIG. 4 is a block diagramof a high pressure dispersion machine, and FIG. 5 is a characteristicdiagram showing an example of viscosity changes by logarithm.

BEST MODE OF CARRYING OUT THE INVENTION Embodiment 1

FIG. 1 is a block diagram of a winding type electric double layercapacitor in an embodiment of the invention. In FIG. 1, referencenumeral 1 is a case, in this case, on the surface of a conductive foil2, a current collector 3 formed by dispersing at least one of ammoniumsalt of carboxy methyl cellulose resin, polyvinyl alcohol, methylcellulose, and hydroxy propyl cellulose resin, together withpolytetrafluoroethylene resin (PTFE) is formed, as a feature of theinvention, at least on one plane of the conductive foil 2 by binding atdensity of 0.35 g/cc or more to 1.50 g/cc or less. A plurality ofconductive foils, that are conductors, forming this current collector 3are wound on a separator 4, and a winding 5 a is formed. A plurality oflead-out electrodes 6 are connected to the plurality of conductive foils2 forming this winding 5 a, and connected to a terminal 8 through asealing material 7. In the actual electric double layer capacitor, thewinding 5 a is sealed in the case 1 together with electrolyte solution.

A further detail is described below. In 500 parts by weight of purifiedwater, 6 parts by weight of polytetrafluoroethylene resin (as dry weightof emulsion with solid content of 50%), and 6 parts by weight of carboxymethyl cellulose are dissolved, and 100 parts by weight of activatedcarbon powder and 10 parts by weight of acetylene black are added, anddispersed uniformly. Thus, an electrode solution was prepared. Bychemical etching, the electrode solution was applied on both sides of aconductive film (100 mm in width, 20 m in length) by using a coatingmachine, and a coat film of 80 microns in thickness on one side wasformed. Thus, a current collector was prepared.

A lead-out electrode was connected to the obtained foil of electrodecoat film, and a specified length was wound on a separator, and put inan aluminum case. As the electrolyte solution, 1 mol/liter of tetraethylammonium tetrafluoroborate -was dissolved in propylene carbonatesolution. This electrolyte solution was input in the aluminum case, andthe current collector was wetted. While disposing a part of the lead-outelectrode, it was sealed by using a rubber packing. In this way, anelectric double layer capacitor was prepared (hereinafter calledinvention 1).

By way of comparison, as a first, prior art, using carboxy methylcellulose, 6 parts by weight is dissolved in 500 parts by weight ofpurified water, and 100 parts by weight of activated carbon powder and10 parts by weight of acetylene black are added, and disperseduniformly, in an attempt to prepare an electrode solution. However,activated carbon, or in particular acetylene black could not bedispersed in the purified water. Accordingly, 300 parts by weight ofethyl alcohol was added and dispersed (aside from alcohol, when ammoniawas added, a similar effect was obtained). This electrode solution(hereinafter called conventional electrode solution) was applied on bothsides of the conductive film same as in the embodiment, and dried, and acoat film of 80 microns in thickness on one side was formed. Further, itwas dried with far infrared rays for 120 minutes at 110 deg. C. Thisfoil of electrode coat film was wound on a separator by the same length(same area) as in the embodiment, and an electric double layer capacitorwas prepared (hereinafter called prior art 1).

For further comparison, as a second prior art, an electrode solution wasprepared by using polytetrafluoroethylene resin only, and it was appliedon both sides of a conductive foil same as in the embodiment, and anelectric double layer capacitor was prepared (hereinafter called priorart 2).

The invention 1, and prior arts 1 and 2 were presented for accelerationtest. As a result, deterioration of characteristic was smaller ininvention 1. Accordingly, by redissolving test of various coat films forforming the current collector in nonaqueous electrolyte solution orwater, the binding strength was measured before and after it. As aresult, in invention 1, there was no abnormality in redissolving test,and the binding strength was not changed before and after redissolvingtest.

In prior arts 1 and 2, on the other hand, when winding the currentcollector, coat film crack or coat film peeling occurred. Or when thefinished current collector was folded and stretched multiple times,crack or peeling did not took place in invention 1, but crack or peelingwas found in prior art 2. In the polytetrafluoroethylene resin alone,there was a problem in forming performance of coat film, and if it isusable in button type or coin type, it is known difficult to apply inwinding type or laminate types. As compared with prior arts 1, 2, it waseasier to remove moisture in the coat film in invention 1. This isconsidered because the polytetrafluoroethylene resin itself does nothave water absorption or water solubility. By combining suchpolytetrafluoroethylene resin (the polytetrafluoroethylene resin itselfdoes not have water absorption or water solubility, and has a properflexibility, but lacks in film forming performance), with other resinmaterial, the physical characteristic of the current collector can beenhanced, and the product reliability is enhanced.

Although the polytetrafluoroethylene resin itself is not soluble inwater, but by dispersing preliminarily in water or solvent in a state ofemulsion, it is easier to handle or manufacture electrode solution. Inthe case of such emulsion type polytetrafluoroethylene resin, it isoften dispersed in purified water by using surface active agent or thelike. Accordingly, depending on the kind of the finishedpolytetrafluoroethylene resin, the pH varies. When manufacturing anelectrode solution of an electric double layer capacitor, a neutral orweak alkaline solution is preferred. Depending on the kind of theactivated carbon used in the electric double layer capacitor, a carboxylgroup may be left over as a residue to surface chemical substanceaccording to the treatment of activated carbon. Such activated carbon iseasily dispersed in a weak alkaline resin solution. However, when theacidity of the resin solution is high, it is hard to disperse theactivated carbon uniformly. Therefore, the pH of the disperse solutionof polytetrafluoroethylene resin is preferred to be 5 or more to 12 orless.

The content of the polytetrafluoroethylene resin in 100 parts by weightof activated carbon is preferred to be 1 part by weight or more to 20parts by weight or less as the solid content of polytetrafluoroethyleneresin (in dry weight). If less than 0.5 part by weight, the effect ofaddition is small, and if more than 25 parts by weight, the capacitorcapacity of the product may be lost.

Incidentally, by using polytetrafluoroethylene resin in emulsion state,the dispersant in the polytetrafluoroethylene resin can be effectivelyutilized, and an electrode solution can be prepared without addingenvironmental loading substance such as alcohol or ammonia. Inparticular, by using water (or purified water) only as the volatilecontent in the electrode solution, the working environments includingcleaning of equipment can be improved. The particle size of thepolytetrafluoroethylene resin is preferred to be 1 micron or less. Iflarger than 1.5 microns, it is hard to disperse uniformly.

As the resin to be mixed with polytetrafluoroethylene resin,water-soluble high polymer materials for general purpose can be used,such as carboxy methyl cellulose, polyvinyl alcohol, methyl cellulose,and hydroxy propyl cellulose. By mixing the polytetrafluoroethyleneresin with such water-soluble high polymer material, both waterproofproperty and binding performance of coat film are achieved. By addingsuch resin, moreover, if the thickness is 0.1 mm or less or if thethickness is 1 mm or more, the current collector can be coated freely ina desired thickness depending on the product. The viscosity can beadjusted easily in a range, for example, from 1 poise or more to 200poise or less. Without adding such resin, the viscosity of the electrodesolution is 0.5 poise or less, and the plasticity (thixotropy) isfurther lowered, and therefore if coated in a thickness of 0.05 mm orless, a thickness of 0.1 mm or more cannot be applied. Other problem isthat the same thickness cannot be formed every time. Thus, by using thepolytetrafluoroethylene resin together with water-soluble high polymersuch as carboxy methyl cellulose, the coat film precision can beenhanced.

In the invention, the density of the current collector is preferred tobe 0.35 g/cc or more to 1.50 g/cc or less. If less than 0.30 g/cc, thedensity of the current collector is low, and crack or other defectshardly occur in the coat film when winding, but when assembled into theproduct, the capacity is lower. If more than 1.55 g/cc, the nonaqueouselectrode solution hardly permeates into the inside of the currentcollector, and when assembled into the product, the capacity is loweredor the impedance is heightened.

Embodiment 2

FIG. 2 explains a mode of evaluating the winding performance of thecurrent collector and conductive foil. In FIG. 2, in a bound state ofthe current collector 3 having activated carbon and conductive agent ofpolytetrafluoroethylene resin and binder resin on the surface of theconductive foil 2, evaluation of winding performance of the currentcollector 3 and conductive film 2 is explained. In FIG. 2, referencenumeral 9 is a round bar. Around the round bar 9, the conductive foil 2cut in a proper width and binding the current collector 3 at least onone surface is wound, and it is evaluated by squeezing the conductivefoil 2 forming the current collector 3 in the direction indicated byarrow with a specific force. By this method of evaluation, the windingperformance of the current collector 3 is evaluated (whether applicablein winding type electric double layer capacitor, or whether capable ofobtaining deflection resistance required even in laminate type electricdouble layer capacitor). In FIG. 2 (A), the-current collector 3 ispeeled off the conductive foil 2, and further the current collector 3itself forms a fracture 10. In FIG. 2 (B), the current collector 3 isnot peeled off the conductive foil 2, and fine cracks 11 are formed onthe surface of the current collector 3. Herein, a great differencebetween the fine cracks 11 and the fracture 10 lies in presence orabsence of interface breakage between the current collector 3 andconductive foil 2. In FIG. 2 (C), the conductive film 2 is not peeledoff the current collector 3, and a normal surface 12 is formed withoutfracture or fine cracks 11.

According to this method of evaluation, in embodiment 2, thick coatingof the current collector coat film by using polytetrafluoroethyleneresin is explained.

First, in 500 parts by weight of purified water, 12 parts by weight ofpolytetrafluoroethylene resin (using emulsion with solid content of30%), and resin having part of carboxy methyl cellulose replaced by NH4ions (hereinafter called CMC-NH4) are dispersed, and further 100 partsby weight of activated carbon powder and 10 parts by weight of acetyleneblack are added, and dispersed uniformly. Thus, an electrode solution isprepared. This electrode solution was applied on a conductive foil,dried, and an electric double layer capacitor was prepared same as inembodiment 1 (hereinafter called invention 2).

By way of comparison, as a prior art, using carboxy methyl cellulose(partly replaced with NH4 ions), an electric double layer capacitor wasprepared (hereinafter called prior art 3).

Finished coat films were compared, and the current collector ofinvention 2 could be wound in a smaller diameter of 1 mm. On the otherhand, in prior art 3, if wound in a smaller diameter than 3 mm, crack orpeeling occurred. Accordingly, the length of the current collector thatcan be wound in the product (aluminum case) is longer in invention 2 ascompared with prior art 3, and the product capacity and energy densitycan be enhanced. Thus, by adding polytetrafluoroethylene resin, theproduct capacity can be heightened. Besides, in order to enhance thewinding performance of prior art 3, in the case of adding a necessaryamount of glycerin in the, electrode solution as a water-solubleplasticizer, the winding diameter was as small as 1 mm, but whenassembled into the product, to the contrary, the capacity value waslowered.

When polytetrafluoroethylene resin is mixed with a conventionalwater-soluble resin, the concentration of the prepared electrodesolution may vary significantly depending on the kind of the addedactivated carbon or conductive agent (in particular, by their particlesize or specific surface area). Accordingly, the viscosity of theelectrode solution is desired to be set in a composition in a range of 1poise or more to 200 poise or less. If less than 0.5 poise, theviscosity is too low, and it is hard to form a coat film in a thicknessof 50 microns or more, and if finished, the thickness difference may belarger than plus or minus 5 microns or more. If the viscosity is morethan 300 poise, although a thick film over 50 microns can be easilyformed, the leveling (the electrode solution itself flowing so as toeliminate uneven coating by the action of gravity) is poor, and theproductivity drops. To manufacture for the application in electricdouble layer capacitor, the thickness difference of current collector(difference between maximum thickness and minimum thickness) is desiredto be 5 microns or less. If exceeding 10 microns, if the currentcollector of a same length is wound, the diameter of the finishedwinding may be different. Accordingly, when applying by using a coatingmachine (doctor blade coater, etc.), as explained herein, by adding awater-soluble high polymer, the viscosity may be optimized to aneasy-to-apply viscosity (preferably about 5 to 100 poise). Moreover, bykeeping the thickness difference of the coat film below 5 microns,stabilization of manufacturing process and decrease of fluctuations ofproducts may be realized. Thus, the fluctuations in capacity value amongproducts may be kept to a minimum limit.

Thus, by the resin containing polytetrafluoroethylene resin, by usingthe activated carbon and conductive agent as the current collector 3,the winding performance can be enhanced. Referring now to FIG. 2, a modeof evaluation of winding performance of the current collector on theconductive foil 2 is described. In FIG. 2, reference numeral 9 is around bar. Around the round bar 9, by winding the conductive foil 2 cutin the product width and binding the current collector 3 at least on onesurface, the winding performance of the current collector 3 isevaluated. In FIG. 2 (A), the current collector 3 is peeled off theconductive foil 2, and further the current collector 3 itself forms afracture 10, and this state is evaluated as x (winding disabled). InFIG. 2 (B), the current collector 3 is not peeled off the conductivefoil 2, and fine cracks 11 are formed on the surface of the currentcollector 3, and this state is evaluated as Δ (inferior in windingperformance). In FIG. 2 (C), the conductive film 2 is not peeled off thecurrent collector 3, and the surface of the current collector 3 is freefrom fracture, crack or damage, and this state is evaluated o (excellentin winding performance). Herein, the current collector 3 was formed onboth sides of the conductive film 2, and both surfaces were evaluatedalternately 10 to 100 times each.

By using a hitherto proposed current collector not containing latex,when the thickness is 50 microns, if the winding diameter was 5 mm, theevaluation was FIG. 2 (C), but when the thickness was increased to 80microns, the winding was sometimes inferior as in FIG. 2 (B). At thethickness of 150 microns or more, if the winding diameter was 5 mm, thewinding was sometimes disabled as in FIG. 2 (A). At the thickness of 50microns, as the winding diameter was decreased to 4 mm, 3 mm, and 2 mm,the phenomenon of inferior winding as in FIG. 2 (B) tended to occur.Concerning such winding performance of the current collector, it isempirically known that it is also influenced by the residual moisture inthe current collector coat film. Accordingly, by adjusting the residualmoisture in the current collector at 30% or more, occurrence of finecracks 11 or fracture 10 in winding may be decreased. But it isdifficult to control the residual moisture accurately, and it was aproblem that there were large effects depending on season and ambienttemperature.

On the other hand, in the case of the resin containingpolytetrafluoroethylene resin of embodiment 2, if the current collectorthickness is increased to 100 microns or 200 microns and the windingdiameter is 2 mm or less, fine cracks 11 or fracture 10 did not occurwhen winding. As a result of similar experiment by varying the residualmoisture of the current collector, it was similarly free from finecracks 11 or fracture 10 at the residual moisture of 5% or less orresidual moisture of 50% or more. Thus, by using the current collectorcontaining polytetrafluoroethylene resin, winding of higher density andfilming of larger thickness of current collector as compared with theprior art are realized.

Embodiment 3

By decreasing the content of polytetrafluoroethylene resin, and usingpolyvinyl alcohol as conventional water-soluble resin, it was attemptedto make insoluble (resistant to water) by polymerizing (curing) thewater-soluble resin. First, in 500 parts by weight of purified water, 2parts by weight of polytetrafluoroethylene resin and 10 parts by weightof polyvinyl alcohol were dissolved, and further zirconia compound wasadded as a polymerizing agent. In this solution, 100 parts by weight ofactivated carbon powder and 10 parts by weight of acetylene black wereadded and dispersed uniformly, and an electrode solution was prepared.This electrode solution was applied on a conductive foil in a thicknessof 80 microns on one side. The resistance to water of this electrodecoat film was tested, and it was found that to be resistant to water(insoluble) when heated for 5 minutes to 10 minutes at temperature of120 deg. C. to 150 deg. C. By thus making resistant to water, theresidual moisture in the coat film was hardly adsorbed. At temperatureexceeding 300 deg. C., since the decomposition of the resin is promoted,the coat film becomes brittle. Without addition of polymerizing agent,meanwhile, the electrode coat film was not sufficiently resistant towear if heated for 12 hours at 130 deg. C. or less.

When using zirconia as the polymerization initiator or reactioninitiator, it is preferred to add by 1 part by weight or more to 10parts by weight or less in 100 parts by weight of the binder, and tomake insoluble in water by drying or heat treatment. If the content issmaller, the water insolubility of the water-soluble resin isinsufficient, and if the content is too large, the productcharacteristics of the electric double layer capacitor (capacity value,energy density, etc.) are lowered. Such polymerization initiator orreaction initiator is preferred to be a stable metal oxide, not beingionized, after reaction. Therefore, if the polymerization initiator orreaction initiator is left over, the characteristics of the electricdouble layer capacitor will not be lowered. Moreover, by using thepolymerization initiator or reaction initiator, various high polymermaterials such as methyl cellulose and hydroxy methyl cellulose may befurther used. In such a case, too, it is preferred to combinepolytetrafluoroethylene resin with these high polymer materials.Incidentally, unreacted zirconia compound is transformed into a stablezirconia oxide by heating in the presence of oxygen, and hence does notreact with residual moisture or nonaqueous electrolyte solution in theelectric double layer capacitor.

Embodiment 4

In embodiment 4, a laminate type electric double layer capacitor isexplained by referring to FIG. 3. In FIG. 3, in a rectangularparallelepiped case 1, a plurality of current collectors 3 formed atleast oh one side of a conductive foil 2 are connected through aseparator 4. By forming in a laminate 5 b, the appearance of the productmay be solid, dead angles are decreased and the effective volume isincreased. As a result, the capacity per unit volume (capacity density)is higher by nearly 30% as compared with the winding type. Moreover, ina product thickness of several millimeters, the product size can beincreased to scores of centimeters square, and it contributes to thinand small design of appliances.

A further detail is described. First, an electric double layer capacitorof ultrathin layer and large laminate type of 1 mm in thickness and 200mm×300 mm in size was fabricated. The product is desired to have acertain flexibility and resistance to deformation. In such a case, in aconventional rigid current collector, there was a risk of breaking orcracking. Accordingly, from the current collector 3 prepared inembodiment 4, a plurality were cut out in a size of 180 mm×280 mm, andthe plurality were laminated through a commercial separator, and sealedin a nonaqueous electrode solution together with lead-out electrode, andan ultrathin electric double layer capacitor was prepared. Thiscapacitor was resistant to bend or warp, and if deflected by force,there was no adverse effect on the electric characteristic orreliability. After such deformation test, the latex part was decomposedand the state of the current collector 3 was inspected, but noabnormality was found.

By way of comparison, using a current collector without undergoing hightension dispersion, a current collector was similarly fabricated, and anelectric double layer capacitor of ultrathin layer and large laminatetype of 1 mm in thickness and 200 mm×300 mm in size was prepared. Inthis case, however, the current collector 3 itself was a still plate,having no flexibility and hardly deflecting. When thus preparedcapacitor was bent slightly, the electric characteristic droppedsuddenly. When analyzed later, it was found that many cracks were formedin the current collector film, and part of the conductive foil wasbroken, and it was nearly shorted partly. Thus, by high tensiondispersion of the electrode solution, fine particles ofpolytetrafluoroethylene resin were dispersed uniformly, and theperformance of the current collector was enhanced.

Meanwhile, by connecting a plurality of such thin electric double layercapacitors in series, and forming into a unit, the dielectric strengthcan be enhanced, and its conversion efficiency can be improved also whenconverting voltage by using a DC-DC converter or the like.

Also by connecting a plurality of such thin electric double layercapacitors in parallel, and forming into a unit, the capacity can beincreased substantially. Also by sorting and ranking the electric doublelayer capacitors, a capacitor of a stabler characteristic may beassembled.

Such ultrathin electric double layer capacitor is easier to lower theESR (equivalent series resistance) as compared with the winding type,and is excellent in frequency characteristic, and hence it may bepreferably used in the personal computer, TV, air conditioner, variousheating appliances, and others. Moreover, voltage drop can be preventedwhere a large current is suddenly required such as in a laser beamprinter

Embodiment 5

Pressing of a current collector containing polytetrafluoroethylene resinwas experimented. As a result, invention 1 was raised in density by 10%or more, at a pressure of half or less as compared with prior arts 1 and2, and was also increased in the product capacity. On the other hand, inthe case of prior arts 1 and 2 not containing polytetrafluoroethyleneresin, the coat film was adhered to the press surface, and peeling ofcoat film occurred. This is considered partly because adhesion of thecurrent collector to the press was lowered (the peeling performance wasimproved) by adding polytetrafluoroethylene resin.

As the conductive agent, carbonaceous conductive materials may be used,such as acetylene black, Ketienblack, and graphite fine powder. Orconductive high polymer such as polypyrol and metal fine powder may beused. At this time, the content of the conductive agent is preferred tobe 2 parts by weight or more to 10 parts by weight or less of 100 partsby weight of activated carbon. If the content of the conductive agent is1 part by weight or less, the conductivity of the electrode coat film islowered, and it is possible that the ESR (equivalent series resistance)or impedance when assembled into the product may be higher. If added by15 parts by weight or more, the content of the activated carbon in theproduct is decreased by the corresponding portion, and the productcapacity may be lowered.

Incidentally, by roughening the surface of the conductive foil used inthe current collector, the binding performance of the electrode coatfilm is heightened and the peeling probability of the coat film may bedecreased. As roughening means, sand blasting process or etching processmay be employed.

Embodiment 6

Embodiment 6 relates to a method of manufacturing an electric doublelayer capacity by forming a current collector containing activatedcarbon and conductive agent, by a resin containing latex, on the surfaceof a conductive foil. As the activated carbon, commercial powder withspecific surface area of 1500 to 2000 square meters/g was used, and as aconductive agent, commercial acetylene black was used. In a mixedaqueous solution of aqueous solution of carboxy methyl cellulose andlatex, the activated carbon and acetylene black were added, anddispersed, and an electrode solution was prepared. This electrodesolution was applied on both sides of a commercial conductive foil in adry thickness of 100 microns on each side. A plurality of the currentcollectors 3 were cut in a specified width as shown in FIG. 1, and woundon a separator 4, starting from the minimum winding diameter of 2 mm andfinishing at final winding diameter of 8 mm, and a winding 5 a wasprepared. Each lead-out electrode 6 was connected to a plurality ofconductive foils forming the winding 5 a, and they were put in acylindrical case 1 of 10 mm in diameter, and impregnated in a specifiedelectrolyte, and sealed with a sealing material 7 with a terminal 8(hereinafter called invention 3).

By way of comparison, in an aqueous solution of carboxy methylcellulose, the activated carbon and acetylene black were added, anddispersed, and an electrode solution was prepared. This electrodesolution was applied on both sides of a commercial conductive foil, in adry thickness of 100 microns on each side. A plurality of the currentcollectors 3 were cut in a specified width as shown in FIG. 1, and itwas attempted to wind them on a separator 4, but when the minimumwinding diameter was 2 mm, phenomena as shown in FIGS. 2 (A) and (B)occurred. Accordingly, instead, starting from the minimum windingdiameter of 5 mm and finishing at final winding diameter of 8 mm, awinding 5 a was prepared. It was put in a cylindrical case of 10 mm indiameter, and an electric double layer capacitor was prepared(hereinafter called prior art 4). As a result of investigation ofcharacteristics of invention 3 and prior art 4, invention 3 was largerin capacity by 10% or more. This is considered because the number ofturns is larger (the length of the current collector is longer) ininvention 3 as compared with prior art 4.

Embodiment 7

In embodiment 7, the composition ratio of latex and various materials isfurther optimized. First, in 500 parts by weight of purified water, 12parts by weight of latex (by dry weight of emulsion with solid contentof 50%) was dispersed, and 100 parts by weight of activated carbonpowder and 10 parts by weight of acetylene black as conductive agentwere further added, and dispersed uniformly, and an electrode solutionwas prepared. This electrode solution was applied on both sides of aconductive foil (width 100 mm, length 20 m) roughened by chemicaletching, by using a coating machine, and a coat film of 80 microns inthickness on each side was formed, and a current collector was prepared.

A lead-out electrode was connected to the obtained foil of electrodecoat film, and wound by a specified length on a separator, and put in analuminum case. In propylene carbonate solution, tetraethyl ammoniumtetrafluoroborate was dissolved by 1 mol/liter, and the obtainedelectrolyte solution was put in the aluminum case, the current collectorwas wetted, and it was sealed with a rubber packing so that part of thelead-out electrode be exposed outside, and an electric double layercapacitor was prepared (hereafter called invention 4).

By way of comparison, using carboxy methyl cellulose as a prior art, 6parts by weight was dissolved in 500 parts by weight of purified water,and further 10 parts by weight of activated carbon powder and 10 partsby weight of acetylene black were added, and dispersed uniformly, and itwas attempted to prepare electrode solution. However, the activatedcarbon, in particular, acetylene black could not be dispersed inpurified water. Accordingly, it was dispersed by further adding 300parts by weight of ethylene alcohol (similar effects were obtained byusing ammonia aside from alcohol). This electrode solution (calledconventional electrode solution hereinafter) was applied on both sidesof the roughened conductive foil, and dried, and a coat film of 80microns in thickness of each side was formed. It was further dried byfar infrared rays for 120 minutes at 110 deg. C. This foil of electrodecoat film was wound on a separator by a same length (same area), andsimilarly an electric double layer capacitor was prepared (hereinaftercalled prior art 5).

As a result of evaluation of invention 4 and prior art 5, invention 4was smaller in deterioration of characteristic. Then, by redissolvingtest of each coat film forming the current collector in nonaqueouselectrolyte solution or water, the binding strength was measured beforeand after it. In the case of invention 4, it was free from abnormalityalso in redissolving test, and the binding strength was not changedbefore and after the redissolving test.

In prior art 5, on the other hand, the current collector partly elutedin the electrolyte solution, and the binding strength was lowered. As aresult of measurement of moisture adsorption of the resin itself (therate of evaporation of water after wetting), it was found that invention4 was less likely to be influenced by the effect of moisture adsorptionas compared with prior art 5. As a result of bending and stretching thecurrent collector multiple times, crack or peeling did not occur ininvention 4, but such crack or peeling phenomenon occurred in prior art5.

Thus, by using latex (since the latex itself has no water absorbingproperty or water solubility), the physical characteristics of thecurrent collector could be enhanced, and the product reliability wasimproved.

Incidentally, the latex itself is an elastic rubber, and by dispersingsuch material in water in emulsion state, it becomes easier to handle orprepare electrode solution. As the latex, aside from the natural latex,synthetic materials may be used such as SBR (styrene butadiene rubber)and NBR (nitrile butadiene rubber). Examples of such synthetic latexalso include butadiene copolymer, styrene butadiene copolymer, andcarboxy denatured styrene butadiene copolymer. The emulsion of suchlatex is often dispersed in emulsion state in water at concentration of30 to 70 wt. %, and therefore when using in electrode solution, it ispreferred to dilute in purified water at specified concentration, andadd activated carbon and conductive agent. In the case of emulsion oflatex used for electrode coat film, the particle size of emulsion ispreferred to be 0.1 micron or less. In the case of electrode solutionprepared by using emulsion with particle size of 0.3 micron or more,coagulation or sedimentation may occur.

The latex is often dispersed in purified water by using surface activeagent or the like. Accordingly, the pH varies depending on the kind offinished latex. When preparing an electrode solution of electric doublelayer capacitor, neutral or weak alkaline solution is preferred.Depending on the kind of the activated carbon used in the electricdouble layer capacitor, carboxyl group as surface chemical substance maybe left over as residue depending on the treatment of activated carbon.Such activated carbon may be easily dispersed in a weak alkalinesolution of resin. However, when the acidity of the resin solution ishigh, it is hard to disperse the activated carbon uniformly.Accordingly, the pH of the disperse solution of latex is preferred to be5 or more to 12 or less.

The content of latex emulsion is preferred to be 4 parts by weight ormore to 200 parts by weight (as dry weight) as latex solid content, in100 parts by weight of activated carbon. When preparing an electrodesolution by using only latex as resin, if less than 3 parts by weight,the adhesion strength is weak. If more than 300 parts by weight, theproduct capacity may be lowered depending on the kind of activatedcarbon.

In this way, by using the latex in emulsion state, the dispersant in thelatex may be utilized effectively, and an electrode solution can beprepared without adding environmental loading substance such as alcoholand ammonia. In particular, by using only water (or purified water) asthe volatile content in the electrode solution, the working environmentincluding cleaning of equipment may be improved.

Embodiment 8

In embodiment 8, a laminate type electric double layer capacitor isexplained by referring to FIG. 3. In FIG. 3, a plurality of currentcollectors 3 containing latex formed at least on one side of aconductive foil 2 are connected in a rectangular parallelepiped case 1,through a separator 4. By forming into a laminate 5 b, the productappearance may be a cube, and dead angles are decreased and effectivevolume is increased, so that the capacity per unit volume (capacitydensity) may be heightened by nearly 30% as compared with the windingtype. Moreover, while keeping the product thickness thinly at severalmillimeters, the product size may be increased to scores of centimeterssquare, which contributes to thinner layer and smaller size of theobject appliance.

A further detail is described below. First, a trial piece of electricdouble layer capacitor of ultrathin layer and large size laminate typeof 1 mm in thickness and 200 mm×300 mm was fabricated. In the case ofembodiment 1, the product is required to have a certain elasticity andresistance to deformation. In such a case, in a conventional rigidcurrent collector, it was often cracked or broken. From the currentcollector 3 prepared in embodiment 8, a plurality of pieces were cut offin dimensions of 180×280 mm, and the plurality were laminated through acommercial separator, and sealed in a nonaqueous electrode solutiontogether with the lead-out electrode, and a ultrathin layer electricdouble layer capacitor was prepared (hereinafter called invention 5).This invention 5 was resistant to bending and warp, and if deflected byforce, adverse effects were not observed in the electric characteristicor reliability. After such deformation test, invention 5 wasdisassembled, and the current collector 3 was investigated, but noabnormality was detected.

By way of comparison, using carboxy methyl cellulose as conventionalcurrent collector, a current collector 3 was prepared similarly, and anelectric double layer capacitor of ultrathin layer and large sizelaminate type of 1 mm in thickness and 200 mm×300 mm was fabricated(hereinafter called prior art 6). In the case of prior art 6, thecurrent collector 3 itself was a stiff plate with no flexibility, hardlydeflecting. Damages often occurred in the current collector 3 as shownin FIG. 2 (A) and FIG. 2 (B). In such prior art 6, if bent slightly, theelectric characteristic dropped suddenly. As known later by analysis,many cracks were formed in the current collector film, and part ofconductive foil was broken, and it was nearly shorted in some parts.Thus, by adding latex to the current collector itself, an electricdouble layer capacitor of ultrathin layer laminate type can be preparedstably.

By connecting a plurality of such thin layer electric double layercapacitors in series to form into a unit, the dielectric strength isheightened, and in the case of voltage conversion by using DC-DCconverter or the like, the conversion efficiency is enhanced.

Also by connecting a plurality of such thin layer electric double layercapacitors in parallel to form into a unit, the capacity can beincreased substantially. Also by sorting and ranking the electric doublelayer capacitors, stable characteristic may be realized.

Such ultrathin layer electric double layer capacitor, as compared withthe winding type, is easier to lower the ESR (equivalent seriesresistance), and is superior in frequency characteristics, so that itcan be used in personal computer, TV, air conditioner, and various airheating machines. Or in the case where a large current is requiredinstantly as in laser beam printer, it can be used in an application forpreventing voltage drop.

Embodiment 9

In 500 parts by weight of purified water, 12 parts by weight of latex(using emulsion with solid content of 30%) and carboxy methyl cellulosepartly replaced with NH4 ions (hereinafter called CMC-NH4) weredispersed, and further 10 parts by weight of activated carbon powder and10 parts by weight of acetylene black were added and disperseduniformly, and an electrode solution was prepared. This electrodesolution was applied on a roughened conductive foil, and dried, and anelectric double layer capacitor was prepared in the same manner as inembodiment 1 (hereinafter called invention 6).

By way of comparison, using carboxy methyl cellulose as prior art(partly replaced with NH4 ions), an electric double layer capacitor wasprepared (hereafter called prior art 7).

As a result of comparison of finished coat films, the current collectorin invention 6 could be wound to a smaller diameter of 1 mm. On theother hand, in the case of prior art 7, if wound to a diameter smallerthan 3 mm, crack or peeling occurred. Therefore, the length of thecurrent collector that can be wound in a product (aluminum case) waslonger in invention 6 as compared with prior art 7, and the productcapacity and energy density could be enhanced.

Meanwhile, in the case of a mixture of latex and conventionalwater-soluble resin, the concentration of the prepared electrodesolution may vary significantly depending on the kind of the activatedcarbon or conductive agent to be added (in particular, the particle sizeand specific surface area of these materials). Accordingly, thecomposition should be preferably set so that the viscosity of theelectrode solution may be in a range of 2 poise or more to 200 poise orless. If less than 0.5 poise, the viscosity is too low to form a coatfilm in a thickness of 50 microns or more, and the thickness differencemay be more than plus or minus 5 microns. If the viscosity is more than300 poise, although it is easy to form a coat film in a thickness of 50microns or more, the leveling (flow of electrode solution itself so asto eliminate uneven coating by the action of gravity) is poor, and theproductivity is lowered. To manufacture as an electric double layercapacitor, the thickness difference of the current collector (differenceof maximum thickness and minimum thickness) is preferred to be 5 micronsor less, and if exceeding 10 microns, if a current collector of a samelength is wound, the diameter of the finished winding may be different.

In the case of the current collector containing latex of the invention,only latex may be used as the binder. When applying the electrodesolution containing latex on the conductive foil, a coating machine suchas doctor blade may be used. Depending on the kind of the coatingmachine, an appropriate electrode solution viscosity may be specified.In such a case, aside from latex, water-soluble high polymer (carboxymethyl cellulose, polyvinyl alcohol, methyl cellulose, hydroxy ethylcellulose, or other water-soluble high polymer) may be added asrequired, and a viscosity suited to application (for example, 5 to 100poise) may be adjusted. As a result, the thickness difference of coatfilm may be kept at a high precision of 5 microns or less, and themanufacturing process may be stabilized, and product fluctuations may bedecreased.

Embodiment 10

It was attempted to make insoluble (resistant to water) by decreasingthe latex resin, increasing the conventional water-soluble resin, andfurther polymerizing (curing) the water-soluble resin. First, in 500parts by weight of purified water, 2 parts by weight of latex and 10parts by weight of polyvinyl resin were dissolved, and further zirconiacompound was added as polymerizing agent. In this mixture, further, 10parts by weight of activated carbon and 10 parts by weight of acetyleneblack were added, and dispersed uniformly, and an electrode solution wasobtained. This electrode solution was applied on a roughened conductivefoil in a thickness of 80 microns on each side. It was attempted to makethis electrode coat film resistant to water, and it was found to beresistant to water (insoluble) when heated for about 5 to 10 minutes attemperature of 120 deg. C. to 150 deg. C. By thus making resistant towater, the residual moisture of the coat film was hardly adsorbed. Attemperature exceeding 300 deg. C., however, since decomposition of theresin is promoted, the coat film becomes brittle. Without addition ofpolymerizing agent, if heated for 12 hours at 130 deg. C. or less, theelectrode coat film was not sufficiently resistant to water

When using zirconia compound as such polymerization initiator orreaction initiator, it is preferred to add by 1 part by weight or moreto 10 parts by weight or less in 100 parts by weight of the binder, andmake insoluble in water by drying or heating. If the addition isinsufficient, the water-soluble resin is not sufficiently insoluble inwater. If the addition is excessive, the product characteristics of theelectric double layer capacitor (capacity value, energy density, etc.)are lowered. As such polymerization initiator or reaction initiator, itis preferred that it is not ionized after reaction but becomes a stablemetal oxide. Consequently, if the polymerization initiator or reactioninitiator is left over, it does not deteriorate the characteristic ofthe electric double layer capacitor. Moreover, by using thepolymerization initiator or reaction initiator, in addition, varioushigh polymer materials can be used such as methyl cellulose andhydroxymethyl cellulose. Even in this case, it is preferred to usetogether with latex. Concerning the unreacted zirconia compound, byheating in the presence of oxygen, it is transformed into a stablezirconia oxide. It does not react with the residual moisture ornonaqueous electrode solution in the electric double layer capacitor.

Incidentally, when the glass transition temperature (a kind of softeningpoint) of latex resin is 20 deg. C. or higher, the flexibility of theobtained current collector or coat film is lowered. Hence, the glasstransition temperature of the latex resin is preferred to be 0 deg. C.or less, more preferably −10 deg. C. or less.

As the resin to be mixed with latex, for example, carboxy methylcellulose, polyvinyl alcohol, methyl cellulose, hydroxy propylcellulose, and other water-soluble high polymer materials may be used.By mixing with such water-soluble high polymer materials, both waterresistance and binding performance of coat film may be realized. Byadding such resin, whether the thickness is less than 0.1 mm or thethickness is more than 1. mm, the viscosity may be adjusted easily in arange of, for example, 1 poise or more to 200 poise or less so that athickness depending on the product may be freely applied. Withoutaddition of such resin, the viscosity of the electrode solution is 0.5poise or less, and the plasticity (thixotropy) is further heightened,and a thickness of 0.05 mm or less may be applied, but a thickness of0.1 mm or more cannot be applied. Or, a same thickness cannot be appliedevery time. Thus, by using latex together with water-soluble highpolymer such as carboxy methyl cellulose, the coat film precision can beenhanced.

In the invention, the density of the current collector is preferred tobe 0.35 g/cc or more to 1.50 g/cc. If less than 0.30 g/cc, the densityof current collector is low, and crack or other defect may hardly occurin the coat film when winding, but the capacity is low when assembledinto product. If more than 1.55 g/cc, the nonaqueous electrode solutionhardly permeates into the current collector, and the capacity is loweredwhen assembled in product, or the impedance may be heightened.

Embodiment 11

Pressing of a current collector (invention 6 of embodiment 9) containinglatex was experimented. As a result, invention 6 was raised in densityby 10% or more, at a pressure of half or less as compared with prior art7. The flexibility or binding strength was not lowered before and afterthe pressing test. The current collector was free from elongation (inparticular, deformation of conductive foil). Thus, by lowering the presspressure or calender pressure, the facility cost can be lowered and theproductivity can be raised. At the same time, elongation of the currentcollector (in particular, deformation of conductive foil) could besuppressed. On the other hand, in the case of prior art 7, by pressing,the flexibility and binding strength of the coat film were lowered.Moreover, when the pressure was raised, the current collector wasdeformed.

As the conductive agent, carbonaceous conductive materials may be used,such as acetylene black, Ketienblack, and graphite fine powder. Orconductive high polymer such as polypyrol and metal fine powder may beused. At this time, the content of the conductive agent is preferred tobe 2 parts by weight or more to 10 parts by weight or less of 100 partsby weight of activated carbon. If the content of the conductive agent is1 part by weight or less, the conductivity of the electrode coat film islowered, and it is possible that the ESR (equivalent series resistance)or impedance when assembled into the product may be higher. If added by15 parts by weight or more, as compared with the rubber materialdissolved in solvent, since the rubber material of the invention is anemulsion, the capacity is not particularly decreased. Accordingly, ifadded by 200 parts by weight or more, the desired product capacity canbe obtained. If added by more than 500 parts by weight, since the amountof activated carbon usable in the product is decreased, and hence theproduct capacity may be lowered.

Embodiment 12

Embodiment 12 explains the result of experiment on particle size oflatex. First, five kinds of latex with particle size of 10 microns, 5microns, 1 micron, 0.1 micron, and 0.01 micron were prepared. Afterfabrication of trial products of current collectors as shown inembodiment 1, when latex of 10 microns and 5 microns in particle sizewas dispersed together with activated carbon powder, aggregates werelikely to be formed, and the electric characteristics of the obtainedelectric double layer capacitor itself were lower than the designvalues. On the other hand, as for three kinds of latex with particlesize of 1 micron, 0.1 micron and 0.01 micron, if dispersed together withactivated carbon powder, aggregates were not formed, and the coatingperformance and mass producibility were excellent, and electriccharacteristics conforming to the design values were obtained. Thus, bydefining the particle size of latex at 1 micron or less, if mixed withactivated carbon or conductive agent, aggregate are hardly formed.Meanwhile, if the particle size of latex is less than several angstroms,the pores of the activated carbon surface are filled up to make it hardto form the electric double layer, and hence, the size is preferred tobe more than 10 angstroms.

Embodiment 13

As the resin in the current collector, only latex resin may be used, butit may be also blended with one or more of carboxy methyl celluloseresin, polyvinyl alcohol, methyl cellulose, and hydroxyethyl cellulose.When the electrode solution is prepared by using latex resin only, theviscosity of the obtained electrode solution is too low, and it may behard to apply. In such a case, by mixing the latex resin with any one ofthe water-soluble resins mentioned above, the viscosity of the electrodesolution may be adjusted.

When mixing such resin and latex resin, first, latex resin (latexaqueous solution) is put in purified water, and dispersed uniformly(until a uniform milky white solution is obtained), and, preferably,resin powder such as carboxy methyl cellulose is added, and stirred, anddissolved. If latex aqueous solution is added in the resin solution, itmay require a considerable labor to disperse latex particles uniformly,and it may lead to aggregation or uneven dispersion.

Such latex particles are in emulsion state dispersed in a solvent mainlycomposed of water containing a slight amount of surface active agent,and the pH of this emulsion is preferred to be 4 or more to 12 or less.If the pH of the emulsion is less than 3 or more than 13, the activatedcarbon may not be dispersed uniformly.

When preparing an electrode solution, by using ion exchange water orpurified water, it is effective to lower the concentration of impurityions which may be part of the cause of lowering the reliability of theelectric double layer capacitor. At this time, by adding ammonia oralcohol, the wettability of the activated carbon may be improved.

Incidentally, according to the Standard Dictionary of Chemical Termsedited by Japan Society of Chemistry (Maruzen, 1991), latex is “formerlydefined to be a natural rubber latex, but ever since development ofsynthetic rubber and synthetic resin emulsion other than rubbercompound, all of them are collectively called latex.” That is, in thisinvention, the latex is not limited to natural rubber and syntheticrubber alone, but includes emulsion of synthetic resin, and such resinscatters among particles of activated carbon, acetylene black,Ketienblack, and others, and they cause the particles to contact witheach other. In the invention, the emulsion is, according to the sameStandard Dictionary of Chemical Terms, “a system of dispersion of otherhardly soluble liquid fine particles in a liquid solute,” but aside fromliquid fine particles, it may be also tacky or elastic gel fineparticles. The solvent may be oil, but considering the environmentalproblems and working efficiency, water or the like is preferred.Dissolving is, according to same Standard Dictionary of Chemical Terms,“a phenomenon of melting of a substance in liquid to be a uniform liquidphase,” and in the resin material dissolved in the conventional solvent,the product characteristic may be lowered in order to cover the surfaceof fine particles of activated carbon or the like (and also fine poreson the surface). However, if the emulsion or latex in the invention isdispersed in the electrode solution, it is predicted to scatter in thefinished current collector 3, and therefore it is low in possibility ofclogging of the activated fine pores with activated carbon.

As a low softening point resin, a resin of which Tg (glass transitiontemperature) is −10 deg. C. or less may be selected, and such resin maybe processed into latex. Low softening point resins include many resinsthat can be polymerized or crosslinked, and by selecting such resins,the product reliability is enhanced. As the low softening point resin ofwhich Tg is −10 deg. C. or less, a resin containing plasticizer may beused, and such examples include vinyl chloride, ethylene-vinyl chloridecopolymer resin, vinylidene chloride latex, chlorinated resin, vinylacetate resin, polyvinyl butyral, polyvinyl formal, bisphenol systemepoxy resin, polyurethane resin and others. Moreover, SBR (styrenebutadiene rubber), butadiene rubber, isoprene rubber, NBR(acrylonitrile-butadiene copolymer rubber), urethane rubber, siliconerubber, acrylic rubber, and various elastomers may be used. Byprocessing such resins to be soluble in water, or fine granular (latex),working efficiency and safety of electrode solution in high pressuredispersion may be enhanced.

Embodiment 14

The viscosity of the electrode solution is preferred to be in a range of1 poise or more to 200 poise or less in consideration of the coatingperformance as current collector. The thickness of the current collectoris preferred to be 20 microns or more, and there is no problem if morethan 500 microns. The thickness difference of the current collector ispreferred to be 5 microns or less, and capacity fluctuations of productare decreased, and stable products are presented.

Together with polytetrafluoroethylene resin, by adding a low softeningpoint resin, it is effective for prevention of crack of coat film. Suchlow softening point resin is preferred to have Tg (glass transitiontemperature) of −10 deg. C. or less. If Tg is more than −10 deg. C., itis stiff at room temperature, and when a current collector is formed,breakage, peeling or fine crack may be formed. Low softening pointresins include many resins that can be polymerized or crosslinked, andby selecting such resins, the product reliability is enhanced. As thelow softening point resin of which Tg (glass transition temperature) is−10 deg. C. or less, a resin containing plasticizer may be used, andsuch examples include vinyl chloride, ethylene-vinyl chloride copolymerresin, vinylidene chloride latex, chlorinated resin, vinyl acetateresin, polyvinyl butyral, polyvinyl formal, bisphenol system epoxyresin, polyurethane resin and others. Moreover, SBR (styrene butadienerubber), butadiene rubber, isoprene rubber, NBR (acrylonitrile-butadienecopolymer rubber), urethane rubber, silicone rubber, acrylic rubber, andvarious elastomers may be used. By processing such resins to be solublein water, or fine granular (latex), working efficiency and safety ofelectrode solution in high pressure dispersion may be enhanced.

Thus, by using latex (since the latex itself has no water absorbingproperty or water solubility), the physical characteristics of thecurrent collector could be enhanced, and the product reliability wasimproved.

Incidentally, the latex itself is an elastic rubber, and by dispersingsuch material in water in emulsion state, it becomes easier to handle orprepare electrode solution. As the latex, aside from the natural latex,synthetic materials may be used such as. SBR (styrene.-butadiene rubber)and NBR (nitrile butadiene rubber). Examples of such synthetic latexalso include butadiene copolymer, styrene butadiene copolymer, andcarboxy denatured styrene butadiene copolymer. The emulsion of suchlatex is often dispersed in emulsion state in water at concentration of30 to 70 wt. %, and therefore when using in electrode solution, it ispreferred to dilute in purified water at specified concentration, andadd activated carbon and conductive agent. In the case of emulsion oflatex used for electrode coat film, the particle size of emulsion ispreferred to be 0.1 micron or less. In the case of electrode solutionprepared by using emulsion with particle size of 0.3 micron or more,coagulation or sedimentation may occur.

The latex is often dispersed in purified water by using surface activeagent or the like. Accordingly, the pH varies depending on the kind offinished latex. When preparing an electrode solution of electric doublelayer capacitor, neutral or weak alkaline solution is preferred.Depending on the kind of the activated carbon used in the electricdouble layer capacitor, carboxyl group as surface chemical substance maybe left over as residue depending on the treatment of activated carbon.Such activated carbon may be easily dispersed in a weak alkalinesolution of resin. However, when the acidity of the resin solution ishigh, it is hard to disperse the activated carbon uniformly.Accordingly, the pH of the disperse solution of latex is preferred to be5 or more to 12 or less.

The content of latex emulsion is preferred to be 1 part by weight ormore to 200 parts by weight (as dry weight) as latex solid content, in100 parts by weight of activated carbon. When preparing an electrodesolution by using only latex as resin, if less than 0.5 part by weight,the adhesion strength is weak. If more than 250 parts by weight, theproduct capacity may be lowered.

Further, by using the latex in emulsion state, the dispersant in thelatex may be utilized effectively, and an electrode solution can beprepared without adding environmental loading substance such as alcoholand ammonia. Thus, the working environment including cleaning ofequipment may be improved.

Incidentally, according to the Standard Dictionary of Chemical Termsedited by Japan Society of Chemistry (Maruzen, 1991), latex is “formerlydefined to be a natural rubber latex, but ever since development ofsynthetic rubber and synthetic resin emulsion other than rubbercompound, all of them are collectively called latex.” That is, in thisinvention, the latex is, not limited to natural rubber and syntheticrubber alone, but includes emulsion of synthetic resin, and such resinscatters among particles of activated..carbon, acetylene black,Ketienblack, and others, and they cause the particles to contact witheach other. In the invention, the emulsion is, according to the sameStandard Dictionary of Chemical Terms, “a system of dispersion of otherhardly soluble liquid fine particles in a liquid solute,” but aside fromliquid fine particles, it may be also tacky or elastic gel fineparticles. The solvent may be oil, but considering the environmentalproblems and working efficiency, water or the like is preferred.Dissolving is, according to same Standard Dictionary of Chemical Terms,“a phenomenon of melting of a substance in liquid to be a uniform liquidphase,” and in the resin material dissolved in the conventional solvent,the product characteristic may be lowered in order to cover the surfaceof fine particles of activated carbon or the like (and also fine poreson the surface). However, if the emulsion or latex in the invention isdispersed in the electrode solution, it is predicted to scatter in thefinished current collector, and therefore it is low in possibility ofclogging of the activated fine pores with activated carbon.

Embodiment 15

In embodiment 15, using latex, results of experiment of high pressuredispersion are shown. In the case of the conventional current collectornot containing latex of which thickness is 50 microns, if the windingdiameter was 5 mm, the result was as shown in FIG. 4 (C). As thethickness was increased to 80 microns, the result was sometimes inferiorwinding (Δ) as in FIG. 4 (B). At the thickness exceeding 150 microns, ifthe winding diameter was 5 mm, it was sometimes impossible to wind (x)as shown in FIG. 4 (A). At the thickness of 50 microns, as the windingdiameter was reduced to 4 mm, 3 mm, and 2 mm, the phenomenon of inferiorwinding (Δ) in FIG. 4 (B) tended to occur. Concerning such windingperformance of the current collector, it is empirically known that it isalso influenced by the residual moisture in the current collector coatfilm. Accordingly, by adjusting the residual moisture in the currentcollector at 30% or more, occurrence of fine cracks 11 or fracture 10 inwinding may be decreased. But it is difficult to control the residualmoisture accurately, and it was a problem that there were large effectsdepending on season and ambient temperature.

On the other hand, in the case of the current collector containing latexof embodiment 3, if the current collector thickness is increased to 100microns or 200 microns and the winding diameter is 2 mm or less, finecracks 11 or fracture 10 did not occur when winding. As a result ofsimilar experiment by varying the residual moisture of the currentcollector, it was similarly free from fine cracks 11 or fracture 10 atthe residual moisture of 5% or less or residual moisture of 50% or more.Thus, by using the current collector containing latex, winding of higherdensity and filming of larger thickness of current collector as comparedwith the prior art are realized.

Embodiment 16

Embodiment 16 relates to a method of manufacturing an electric doublelayer capacity by forming a current collector containing activatedcarbon and conductive agent, by a resin containing latex, on the surfaceof a conductive foil. As the activated carbon, commercial powder withspecific surface area of 1500 to 2000 square meters/g was used, and as aconductive agent, commercial acetylene black was used. In a mixedaqueous solution of aqueous solution of carboxy methyl cellulose andlatex, the activated carbon and acetylene black were added, anddispersed at high pressure, and an electrode solution was prepared. Thiselectrode solution was applied on both sides of a commercial conductivefoil in a dry thickness of 100 microns on each side. A plurality of thecurrent collectors 3 were cut in a specified width as shown in FIG. 1,and wound on a separator 4, starting from the minimum winding diameterof 2 mm and finishing at final winding diameter of 8 mm, and a winding 5a was prepared Each lead-out electrode 6 was connected to a plurality ofconductive foils forming the winding 5 a, and they were put in acylindrical case 1 of 10 mm in diameter, and impregnated in a specifiedelectrolyte, and sealed with a sealing material 7 with a terminal 8(hereinafter called invention 7).

By way of comparison, in an aqueous solution of carboxy methylcellulose, the activated carbon and acetylene black were added, anddispersed at high pressure, and an electrode solution was prepared. Thiselectrode solution was applied on both sides of a commercial conductivefoil, in a dry thickness of 100 microns on each side. A plurality of thecurrent collectors 3 were cut in a specified width as shown in FIG. 1,and it was attempted to wind them on a separator 4, but when the minimumwinding diameter was 2 mm, phenomena as shown in FIG. 4 (A) and FIG. 4(B) occurred. Accordingly, instead, starting from the minimum windingdiameter of 5 mm and finishing at final winding diameter of 8 mm, awinding 9 was prepared. It was similarly put in a cylindrical case of 10mm in diameter, and an electric double layer capacitor was prepared(hereinafter called prior art 8). As a result of investigation ofcharacteristics of invention 7 and prior art 8, invention 7 was largerin capacity by 10% or more. This is considered because the number ofturns is larger (the length of the current collector is longer) in thelatex product as compared with prior art 8.

A further detail is described below. In 500 parts by weight of purifiedwater, 12 parts by weight of latex (by dry weight of emulsion with solidcontent of 50%) was dispersed, and further 100 parts by weight ofactivated carbon powder and 10 parts by weight of acetylene black asconductive agent were added, and dispersed at high pressure, and anelectrode solution was prepared.

Thus dispersed electrode solution was applied on both sides of aconductive foil (width 100 mm, length 20 m) roughened by chemicaletching, by using a coating machine, and a coat film of 80 microns inthickness on each side was formed, and a current collector 3 wasprepared.

A lead-out electrode was connected to the obtained foil of electrodecoat film, and wound by a specified length on a separator, and put in analuminum case. In propylene carbonate solution, tetraethyl ammoniumtetrafluoroborate was dissolved by 1 mol/liter, and the obtainedelectrolyte solution was put in the aluminum case, the current collectorwas wetted, and it was sealed with a rubber packing so that part of thelead-out electrode be exposed outside, and an electric double layercapacitor was prepared (hereafter called invention 8).

By way of comparison, using carboxy methyl cellulose as a prior art, 6parts by weight was dissolved in 500 parts by weight of purified water,and further 10 parts by weight of activated carbon powder and 10 partsby weight of acetylene black were added, and dispersed uniformly, and itwas attempted to prepare electrode solution. However, the activatedcarbon, in particular, acetylene black could not be dispersed inpurified water. Accordingly, it was dispersed by further adding 300parts by weight of ethylene alcohol (similar effects were obtained byusing ammonia aside from alcohol). This electrode solution (calledconventional electrode solution hereinafter) was applied on both sidesof the roughened conductive foil, and dried, and a coat film of 80microns in thickness of each side was formed. It was further dried byfar infrared rays for 120 minutes at 110 deg. C. This foil of electrodecoat film was wound on a separator by a same length (same area), and anelectric double layer capacitor was prepared (hereinafter called priorart 9).

As a result of acceleration test of invention 8 and prior art 9,invention 8 was smaller in deterioration of characteristic. Then, byredissolving test of each coat film forming the current collector innonaqueous electrolyte solution or water, the binding strength wasmeasured before and after it. In the case of the invention, it was freefrom abnormality also in redissolving test, and the binding strength wasnot changed before and after the redissolving test.

In prior art 9, on the other hand, redissolving was observed, and thebinding strength was lowered after redissolving test. As a result ofmeasurement of moisture adsorption of the resin itself (the rate ofevaporation of water after wetting), it was found that invention 8 wassmaller in moisture absorption than prior art 9 by one digit or more. Asa result of bending and stretching the current collector multiple times,crack or peeling did not occur in invention 8, but such crack or peelingphenomenon occurred in prior art 9.

Embodiment 17

In 500 parts by weight of purified water, 12 parts by weight of latex(using emulsion with solid content of 30%) and carboxy methyl cellulosepartly replaced with NH4 ions (hereinafter called CMC-NH4) weredispersed, and further 10 parts by weight of activated carbon powder and10 parts by weight of acetylene black were added and disperseduniformly, and an electrode solution was prepared. For this dispersion,a high pressure dispersion machine as shown in FIG. 4 was used. In FIG.4, reference numeral 13 is an inlet, through which the electrodesolution after preliminary kneading is charged. Reference numeral 14 isa pressure unit, which pressurizes the charged electrode solution to ahigh pressure of over 100 kg/cm² by a hydraulic pump or the like.Reference numeral 15 is a dispersion mixer, which disperses by sprayingthe electrode ink at high pressure to a special jig, or collidingelectrode solutions ejected at high pressure from a plurality ofcapillaries with each other. In the pressure unit, the electrodesolution is boosted to a high pressure of at least over 100 kg/cm². Thepressure at this time of dispersion can be monitored by mounting apressure gauge on the pressure unit 14 (or between the pressure unit 14and the dispersion mixer 15). The inside of the dispersion mixer 15 ispartly formed of diamond, ceramic or cemented carbide, so that it can beprotected from abrasion. The electrode solution pressurized over 100kg/cm² is introduced into the dispersion mixer, and the liquids arecollided with each other (or the liquid is collided against the jig) ata speed over the sonic speed to be dispersed. The electrode solutionthus dispersed at high pressure is discharged from an outlet 4. As suchmachine, a pressure type homogenizer manufactured by Gorin, U. S., maybe used. By using such machine, by dispersing while applying a highpressure over 100 kg/cm² (or over 3000 kg/cm² depending on machinespecification) to the electrode solution, the density of the coat filmof current collector may be easily raised over 0.50 g/cc. In order toextend the life of the dispersion machine and stabilize dispersion whileavoiding entry of impurities into the electrode solution, the dispersionmixer should be preferably made of diamond, ceramic or cemented carbide.

This electrode solution was applied on a roughened conductive foil, anddried, and an electric double layer capacitor was prepared in the samemanner as in embodiment 1 (hereinafter called invention 9).

By way of comparison, using carboxy methyl cellulose as prior art(partly replaced with NH4 ions), an electric double layer capacitor wasprepared without adding latex emulsion (hereafter called prior art 10).

As a result of comparison of finished coat films, the current collectorin invention 9 could be wound to a smaller diameter of 1 mm. On theother hand, in the case of prior art 10, if wound to a diameter smallerthan 3 mm, crack or peeling occurred. Therefore, the length of thecurrent collector that can be wound in a product (aluminum case) waslonger in invention 9 as compared with prior art 10, and the productcapacity and energy density could be enhanced.

Meanwhile, in the case of a mixture of latex and conventionalwater-soluble resin, the concentration of the prepared electrodesolution may vary significantly depending on the kind of the activatedcarbon or conductive agent to be added (in particular, the particle sizeand specific surface area of these materials). Accordingly, thecomposition should be preferably set so that the viscosity of theelectrode solution may be in a range of 1 poise or more to 200 poise orless. If less than 0.5 poise, the viscosity is too low to form a coatfilm in a thickness of 50 microns or more, and the thickness differencemay be more than plus or minus 5 microns. If the viscosity is more than300 poise, although it is easy to form a coat film in a thickness of 50microns or more, the leveling (flow of electrode solution itself so asto eliminate uneven coating by the action of gravity) is poor, and theproductivity is lowered. To manufacture as an electric double layercapacitor, the thickness difference of the current collector (differenceof maximum thickness and minimum thickness) is preferred to be 5 micronsor less. If exceeding 10 microns, when a current collector of a samelength is wound, the diameter of the finished winding may be different.Hence, when applying by using a coating machine (doctor blade coater,etc.), as explained herein, by adding water-soluble high polymer, theviscosity can be optimized to an easily applicable viscosity (preferablyabout 2 poise to 100 poise), and the thickness difference of coat film.can -be suppressed within 5 microns, so that stabilization ofmanufacturing process and decrease of product fluctuations may berealized.

As a conventional method of dispersion of electrode solution, as aresult of experiment by using rotary homogenizer, ultrasonichomogenizer, and various mixers, ball mills and sand mills, the densityof coat film was about 0.25 g/cc to 0.30 g/cc. On the other hand, thecoat film density by high pressure dispersion was 0.50 g/cc to 0.65g/cc, and the product capacity and density could be notably improved. Byway of comparison, an ultrasonic homogenizer was used, but the coat filmdensity was hardly increased, and its dispersion effect was notrecognized.

In the case of latex, various surface active agents are often added asstabilizer. Accordingly, in the conventional methods of dispersion(various mixers, ball mill, sand mill, etc.), the electrode solution isstirred together with air, and hence bubbles are likely to be formed.The bubbles formed in the electrode solution are hardly removedcompletely if treated in vacuum, and are left over in the coat film ofthe current collector (causing to lower the density or lower thecapacity), and spots are left over on the dried surface. Anyway, theproduct capacity and density are lowered. On the other hand, in the caseof high pressure dispersion, the electrode solutions impinge with eachother at high pressure (without contacting with air), or hit against acollision plate to be dispersed, so that bubbles are hardly formed.

By mixing latex in electrode coat film, the flexibility of coat film andbending strength could be substantially improved. If the thickness ofcoat film was Increased over 500 microns (to about 5 mm), a specifiedproduct could be manufactured without causing defects such as crack(coat film cracking or coat film peeling) when winding. Since bothflexibility and binding strength of coat film could be notably improvedat the same time, processing by press or calender was possible whilesuppressing the deformation of conductive foil to a minimum limit. As aresult, the coat film density could be easily increased enough over 0.40g/cc, that is, up to 0.75 or 0.95, and the product performance wasenhanced. Incidentally, when the coat film density was over 1.50 g/cc,the product capacity dropped. This is considered because the density wastoo high to fill the inside of the current collector with nonaqueouselectrode solution (and ions) for forming the electric double layer.

Embodiment 18

It was attempted to make insoluble (resistant to water) by decreasingthe latex resin, increasing the conventional water-soluble resin, andfurther polymerizing (curing) the water-soluble resin. First, in 500parts by weight of purified water, 2 parts by weight of latex and 10parts by weight of polyvinyl alcohol resin were dissolved, and furtherzirconia compound was added as polymerizing agent. In this mixture,further, 10 parts by weight of activated carbon powder and 10 parts byweight of acetylene black were added, and dispersed uniformly, and anelectrode solution was obtained. This electrode solution was applied ona roughened conductive foil in a thickness of 80 microns on each side.It was attempted to make this electrode coat film resistant to water,and it was found to be resistant to water (insoluble) when heated forabout 5 to 10 minutes at temperature of 120 deg. C. to 150 deg. C. Bythus making resistant to water, the residual moisture of the coat filmwas hardly adsorbed. At temperature exceeding 300 deg. C., however,since decomposition of the resin is promoted, the coat film becomesbrittle. Without addition of polymerizing agent, if heated for 12 hoursat 130 deg. C. or less, the electrode coat film was not sufficientlyresistant to water

When using zirconia compound as polymerization initiator or reactioninitiator, it is preferred to add by 1 part by weight or more to 10parts by weight or less in 100 parts by weight of the binders and makeinsoluble in water by drying or heating. If the addition isinsufficient, the water-soluble resin is not sufficiently insoluble inwater. If the addition is excessive, the product characteristics of theelectric double layer capacitor (capacity value, energy density, etc.)are lowered. As such polymerization initiator or reaction initiator, itis preferred that it is not ionized after reaction but becomes a stablemetal oxide. Consequently, if the polymerization initiator or reactioninitiator is left over, it does not deteriorate the characteristic ofthe electric double layer capacitor. Moreover, by using thepolymerization initiator or reaction initiator, in addition, varioushigh polymer materials can be used such as methyl cellulose andhydroxymethyl cellulose. Even in this case, it is preferred to usetogether with latex. The unreacted zirconia compound is, by heating inthe presence of oxygen, transformed into a stable zirconia oxide. Itdoes not react with the residual moisture or nonaqueous electrodesolution in the electric double layer capacitor.

Incidentally, when the glass transition temperature (a kind of softeningpoint) of latex resin is 20 deg. C. or higher, the flexibility of theobtained current collector or coat film is lowered. Hence, the glasstransition temperature of the latex resin is preferred to be 0 deg. C.or less, more preferably −10 deg. C. or less.

Embodiment 19

Pressing of a current collector containing latex was experimented. Inthe case of current collector containing latex, as compared with thecurrent collector without latex, the density was raised by 10% or moreat a pressure of half or less. The flexibility or binding strength wasnot lowered before and after the pressing test. The current collectorwas also free from elongation (in particular, deformation of conductivefoil). Thus, by lowering the press pressure or calender pressure, thefacility cost can be lowered and the productivity can be raised, whilethe elongation of the current collector (in particular, deformation ofconductive foil) could be suppressed. On the other hand, in the case ofthe prior art, by pressing, the flexibility and binding strength of thecoat film were lowered. Moreover, when the, pressure was raised, thecurrent collector was deformed.

As the conductive agent, carbonaceous conductive materials may be used,such as acetylene black, Ketienblack, and graphite fine powder. Orconductive high polymer such as polypyrol and metal fine powder may beused. At this time, the content of the conductive agent is preferred tobe 2 parts by weight or more to 10 parts by weight or less of 100 partsby weight of activated carbon. If the content of the conductive agent is1 part by weight or less, the conductivity of the electrode coat film islowered, and it is possible that the ESR (equivalent series resistance)or impedance when assembled into the product may be higher. If added by15 parts by weight or more, the amount of activated carbon usable in theproduct is decreased, and hence the product capacity may be lowered.

Meanwhile, the coat film density varies also with the mean particle sizeor particle size distribution of the activated carbon being used.Anyway, however, in the case of high pressure dispersion method, thecoat film density could be increased by 10% to 30%, and the productcapacity could be raised by 50% or more.

The pressure of the high pressure dispersion machine is required to bemore than 100 kg/cm². At under 80 kg/cm², the pressure in insufficient,and the effect of dispersion is often insufficient. The dispersionpressure is preferred to be 250 kg/cm² or more, or 500 kg/cm² or more.In the case of such high pressure dispersion, the electrode solution maygenerate heat by about 50 deg. C. or 80 deg. C., which may cause lotfluctuations of the electrode solution. It is hence preferred to combinewith a water cooling mechanism for minimizing the heat generation ofelectrode solution. It is also possible to use a superhigh pressuredispersion machine capable of exceeding over 1000 kg/cm². The number oftimes of dispersion is not limited to one only. By repeating dispersionof specified electrode solution a plurality of times by a samedispersion machine, the quality of the electrode solution can bestabilized. If the dispersion pressure pulsates (the pressure rising andfalling regularly), by dispersing repeatedly a plurality of times, thedegree of dispersion can be stabilized.

Aside from the winding type electric double layer capacitor, needless tosay, it can be also applied to the laminate type electric double layercapacitor. Moreover, whether winding type or laminate type, byconnecting a plurality in series, the capacity is enhanced andequivalent series resistance can be decreased, so that a large currentmay be taken out in a short time.

Similarly, whether winding type or laminate type, by connecting aplurality in parallel, the equivalent series resistance can bedecreased, so that a large current may be taken out in a short time.

Incidentally, according to the Standard Dictionary of Chemical Termsedited by Japan Society of Chemistry (Maruzen, 1991), latex is “formerlydefined to be a natural rubber latex, but ever since development ofsynthetic rubber and synthetic resin emulsion other than rubbercompound, all of them are collectively called latex.” That is, in thisinvention, the latex is not limited to natural rubber and syntheticrubber alone, but includes emulsion of synthetic resin, and such resinscatters among particles of activated carbon, acetylene black,Ketienblack, and others, and they cause the particles to contact witheach other. In the invention, the emulsion is, according to the sameStandard Dictionary of Chemical Terms, “a system of dispersion of otherhardly soluble liquid fine particles in a liquid solute,” but aside fromliquid fine particles, it may be also tacky or elastic gel fineparticles. The solvent may be oil, but considering the environmentalproblems and working efficiency, water or the like is preferred.Dissolving is, according to same Standard Dictionary of Chemical Terms,“a phenomenon of melting of a substance in liquid to be a uniform liquidphase,” and in the resin material dissolved in the conventional solvent,the product characteristic may be lowered in order to cover the surfaceof fine particles of activated carbon or the like (and also fine poreson the surface). However, if the emulsion or latex in the invention isdispersed in the electrode solution, it is predicted to scatter in thefinished current collector 7, and therefore it is low in possibility ofclogging of the activated fine pores with activated carbon.

Embodiment 20

In embodiment 20, it was attempted to increase the thickness of thecurrent collector. In the case of a thick current collector, the problemis occurrence of breakage or crack when winding. FIG. 2 shows an exampleof method of evaluation of winding performance. In FIG. 2, referencenumeral 9 is a round bar, and around the round bar 9, the conductivefoil 2 cut in a product width and binding the current collector 3 atleast on one surface is wound, and the winding performance of thecurrent collector 3 is evaluated. In FIG. 2 (A), the current collector 3is peeled off the conductive foil 2, and further the current collector 3itself forms a fracture 10, and this state corresponds to evaluation ofx (winding disabled). In FIG. 2 (B), the current collector 3 is notpeeled off the conductive foil 2, and fine cracks 11 are formed on thesurface of the current collector 3, and this state corresponds toevaluation of Δ (inferior in winding performance). In FIG. 2 (C), theconductive film 2 is not peeled off the current collector 3, and thesurface of the current collector 3 is without fracture 10, cracks 11 orother damage, and this state corresponds to evaluation of o (excellentin winding performance). This performance was evaluated 10 times/100times each alternately on both sides by forming the current collector 7on both sides of the conductive foil 6.

A further detail is described below. In purified water, low softeningpoint resin was dissolved, and activated carbon powder, and acetyleneblack as conductive agent were added, and stirred sufficiently, and anelectrode solution was prepared. This electrode solution was dispersedseveral times by using a high pressure dispersion machine as shown inFIG. 4. Same as in embodiment 1, by high pressure dispersion of theelectrode solution, the viscosity was substantially lowered. Theprepared electrode solution (corresponding to 18 in FIG. 5) wasfiltered, and applied directly on the conductive foil in a dry thicknessof 500 Microns on each side (hereinafter called invention 10).

By way of comparison, the electrode solution before passing through thehigh pressure dispersion machine (corresponding to 17 in FIG. 5) wasfiltered, and directly applied on the conductive foil in a dry thicknessof 500 micron on each side (hereinafter called prior art 11). Thesecurrent collectors were evaluated as shown in FIG. 2. As a result, allsamples of invention 10 were evaluated as (C). In prior art 11, on theother hand, the evaluation was (A) or (B), while (C) was not obtained.As a result of observation of the section of each current collector bySEM (scanning electron microscope), as compared with invention 10, priorart 11 was characterized by uneven density (and coarseness) inside thecoat film of the current collector, which was estimated to be a maincause of difference in winding performance. By winding thus preparedinvention 10, a winding 9 was completed, and an electric double layercapacitor as shown in FIG. 1 was fabricated. In prior art 11, however,the coat film was broken when winding, and winding 5 a could not beformed. As a result, an electric double layer capacitor could not beobtained.

As a low softening point resin, a resin of which Tg (glass transitiontemperature) is −10 deg. C. or less is desired. The resin of which Tg is−10 deg. C. or more is stiff at room temperature, and breakage, peelingor fine crack may be formed when a current collector is formed. Such lowsoftening point resins include many resins that can be polymerized orcrosslinked, and by selecting such resins, the product reliability isenhanced. As the low softening point resin of which Tg (glass transitiontemperature) is −10 deg. C. or less, a resin containing plasticizer maybe used, and such examples include vinyl chloride, ethylene-vinylchloride copolymer resin, vinylidene chloride latex, chlorinated resin,vinyl acetate resin, polyvinyl butyral, polyvinyl formal, bisphenolsystem epoxy resin, polyurethane resin and others. Moreover, SBR(styrene-butadiene rubber), butadiene-rubber, isoprene rubber, NBR(acrylonitrile-butadiene copolymer rubber), urethane rubber, siliconerubber, acrylic rubber, and various elastomers may be used. Byprocessing such resins to be soluble in water, or fine granular (latex),working efficiency and safety of electrode solution in high pressuredispersion may be enhanced.

Embodiment 21

FIG. 4 is a conceptual diagram of a high pressure dispersion machine. InFIG. 4, the electrode solution charged from an inlet 13 is pressurizedto a pressure over 100 kg/cm² in a pressure unit 14, dispersed underpressure in a dispersion mixer 15, and discharged from an outlet 16.This electrode solution is applied on a conductive foil, and a currentcollector is formed. FIG. 1 shows a structural diagram of a winding typeelectric double layer capacitor fabricated by using this currentcollector. In FIG. 1, activated carbon and conductive agent are bound onthe surface of a conductive foil 2 by a binder resin as a currentcollector 3 in a case 1. A plurality of conductive foils 2 forming thiscurrent collector 3 are wound on a separator 4, and a winding 5 a isformed. A plurality of lead-out electrodes 6 are connected to theplurality of conductive foils 6 forming this winding 5 a, and connectedto a terminal 8 through a sealing material 7. In an actual electricdouble layer capacitor, a winding 9 is sealed in the case 1 togetherwith an electrolyte solution.

A further detail is described below. In purified water, carboxy methylcellulose resin was dissolved, and activated carbon powder and acetyleneblack as conductive agent were added, and stirred sufficiently, and anelectrode solution was obtained. This electrode solution was dispersedseveral times by using the high pressure dispersion machine shown inFIG. 4. As a result, the viscosity of the electrode solution was notablylowered. FIG. 4 shows an example of changes of viscosity in alogarithmic graph. Reference numeral 17 shows the viscosity of theelectrode solution before treatment of high pressure dispersion, and 18shows the viscosity of the electrode solution after treatment of highpressure dispersion. Thus, by high pressure dispersion treatment, theviscosity of the electrode solution can be substantially decreased. Theelectrode solution thus prepared (corresponding to 14 in FIG. 3) wasfiltered, and directly applied on the conductive film in a dry thicknessof 50 microns on each side. Finally, by assembling as shown in FIG. 2,and injecting specified electrolyte solution, a product was fabricated(hereinafter called invention 11).

By way of comparison, the electrode solution before passing through thehigh pressure dispersion machine (corresponding to p13 in FIG. 3) wasfiltered and directly applied on the conductive foil in a dry thicknessof 50 microns on each side. Finally, by assembling as shown in FIG. 2,and injecting specified electrolyte solution, a product was obtained(hereinafter called prior art 12). As a result of measurement ofelectric characteristics of thus prepared samples, the capacity was morethan 50% higher in invention 11 as compared with prior art 12. Moreover,as compared with the prior art, invention 11 was lowered to half or lessin the impedance (and equivalent series resistance). Thus, by highpressure dispersion, the capacity and impedance were notably improved.Also as a result of evaluation of reliability of these samples, noproblem was found.

To see why the characteristics are so different between the samplesmanufactured from the same materials, the samples were disassembled andinvestigated. As a result of measurement of density of each currentcollector, it was 0.30 g/cc in prior art 12, and 0.45 g/cc in theinvention. It was thus found that the activated carbon and conductiveagent were more intensified in density by high pressure dispersion.

Embodiment 22

Embodiment 22 explains the mode of preparing a specified electrodesolution (and specified current collector coat film) by using highpressure dispersion machine, without adding alcohol, ammonia or thelike. Thus, by using only purified water (or ion exchange water) as thesolvent, exhaust of organic solvent from the coating machine iseliminated, and the product can be manufactured while taking theenvironments into consideration. It was further dispersed by using thehigh pressure dispersion machine shown in FIG. 2. FIG. 2 shows aconceptual diagram of the high pressure dispersion machine. In FIG. 2,the electrode solution charged from the inlet 10 is pressurized to apressure over 100 kg/cm² in the pressure unit 11, and is dispersed athigh pressure in the dispersion mixer 12, and is discharge from theoutlet 13. Such dispersion is repeated a plurality of times depending onthe necessity.

First, in the procedure shown in embodiment 1, without adding alcohol,ammonia or the like, in a resin solution composed ofpolytetrafluoroethylene resin in emulsion state dispersed in water in aparticle size of 1 micron or less, activated carbon and conductive agentwere dispersed, and a specified electrode solution was prepared. As aresult of applying this electrode solution in a specified thickness ascurrent collector, the density was 0.30 to 0.35 g/cc, and the surfacewas rough with multiple aggregates left over. As a result of analysis ofthese aggregates, the fracture was white and the aggregates were knownto be polytetrafluoroethylene resin. It is thus known thatpolytetrafluoroethylene resin is likely to be aggregated. Concerningthis electrode solution, by devising the method of dispersion, thedispersion of polytetrafluoroethylene resin was enhanced, and a currentcollector of high density and smooth surface was formed. This electrodesolution was dispersed repeatedly a plurality of times by using thedispersion machine in FIG. 3. As a result, the viscosity of theelectrode solution was less than half, and when measured by using aparticle size distribution meter, it was found to be dispersed veryhighly. Using this electrode solution, as a result of application on theconductive foil in a specified thickness, the density was 0.40 to 0.70g/cc, and the surface was very smooth and glossy. Assembling each sampleinto product, the capacity and impedance were measured, and the capacitywas higher by 50% or more and the impedance was lowered by 30% in thesamples of high pressure dispersion as compared with the controlsamples.

Thus, in spite of the same composition of electrode solution, by usingsuch high pressure dispersion machine, a large effect was noted also inthe electrode solution inferior in dispersion performance.

As such high pressure dispersion machine, various products are availablecommercially, but most applications are used in re-dispersion of milk orpreparation of various emulsions, and no example is known in theapplication of preparation of electrode solution. The high pressuredispersion machine for use in preparation of electrode solution ispreferred to comprise at least a pressurizing unit for pressurizing theelectrode solution to a pressure of 100 kg/cm², and a dispersion mixermade of diamond, ceramic or cemented carbide. By using such hardmaterial in members of the high pressure dispersion machine as required,the maintenance of the equipment is easy, and stability of product andreduction of cost are realized.

INDUSTRIAL APPLICABILITY

Thus, by employing the manufacturing method of electric double layercapacitor of the invention, the flexibility, thick coating performanceand winding performance of the current collector are improved, and thecapacity and density of the current collector can be notably enhanced,and the problems of the electric double layer capacitor about largersize, larger capacity and lower cost can be solved.

REFERENCE NUMERALS

1 Case

2 Conductive box

3 Current collector

4 Separator

5 Winding

5 a Laminate

6 Lead-out electrode

7 Sealing material

8 Terminal

9 Round bar

10 Fracture

11 Fine crack

12 Normal surface

13 Inlet

14 Pressure unit

15 Dispersion mixer

16 Outlet

What is claimed is:
 1. An electric double layer capacitor wherein acurrent collector composed of activated carbon, conductive agent, atleast one kind of ammonium salt of carboxyl methyl cellulose resin,polyvinyl alcohol, methyl cellulose and hydroxy propyl cellulose resin,and polytetrafluoroethylene resin dispersed together is formed on atleast one plane of a conductive foil at a density in the range of 0.35g/cc to 1.50 g/cc, and a plurality of said conductive foils are wound orlaminated on a separator, and sealed in a nonaqueous electrode solutiontogether with lead-out electrodes.
 2. An electric double layer capacitorwherein a current collector composed of activated carbon, conductiveagent, at least one kind of ammonium salt of carboxyl methyl celluloseresin, polyvinyl alcohol, methyl cellulose and hydroxy propyl celluloseresin, and latex resin dispersed together is formed on at least oneplane of a conductive foil at a density in the range of 0.35 g/cc to1.50 g/cc, and a plurality of said conductive foils are wound orlaminated on a separator, and sealed in a nonaqueous electrode solutiontogether with lead-out electrodes.
 3. An electric double layer capacitorwherein a current collector composed of activated carbon, conductiveagent, at least one kind of ammonium salt of carboxyl methyl celluloseresin, polyvinyl alcohol, methyl cellulose and hydroxy propyl celluloseresin, and low softening point resin dispersed together is formed on atleast one plane of a conductive foil at a density in the range of 0.35g/cc to 1.50 g/cc, and a plurality of said conductive foils are wound orlaminated on a separator, and sealed in a nonaqueous electrode solutiontogether with lead-out electrodes.
 4. An electric double layer capacitorwherein a current collector composed of activated carbon, conductiveagent, and at least one resin or more of ammonium salt of carboxylmethyl cellulose resin, polyvinyl alcohol, methyl cellulose, hydroxypropyl cellulose resin, low softening point resin,polytetrafluoroethylene resin and latex dispersed together is formed onat least one plane of a conductive foil at a density in the range of0.35 g/cc to 1.50 g/cc, zirconia or zirconia oxide is contained in saidcurrent collector by 1 part by weight to 10 parts by weight in 100 partsby weight of the resin, and a plurality of said conductive foils arewound or laminated on a separator, and sealed in a nonaqueous electrodesolution together with lead-out electrodes.
 5. A manufacturing method ofelectric double layer capacitor comprising: preparing an electrodesolution by dispersing activated carbon and conductive agent, in a resinsolution composed of an aqueous solution of at least one resin ofcarboxyl methyl cellulose resin, polyvinyl alcohol, methyl cellulose,hydroxy propyl cellulose resin and latex, and polytetrafluoroethyleneresin in emulsion state dispersed in water in a particle size of 1micron or less, dispersing at pressure of more than 100 kg/cm² by usinga high pressure dispersion machine, applying said electrode solution ona conductive foil in a specified thickness, and drying to prepare acurrent collector, winding or laminating said current collector on aseparator, and sealing in a nonaqueous electrode solution together withlead-out electrodes.
 6. A manufacturing method of electric double layercapacitor comprising: preparing an electrode solution by dispersing abinder resin, in purified water or ion exchange water, together withactivated carbon and conductive agent, at a pressure of more than 100kg/cm² by using a high pressure dispersion machine, applying saidelectrode solution on a conductive foil as a coat film, and drying toprepare a current collector, winding or laminating said currentcollector on a separator, and sealing in a nonaqueous electrode solutiontogether with lead-out electrodes.
 7. A manufacturing method of electricdouble layer capacitor comprising: dissolving or dispersing at least oneresin of carboxyl methyl cellulose resin, polyvinyl alcohol, methylcellulose and hydroxy propyl cellulose, in water, together with fineparticles of latex or polytetrafluoroethylene resin, then, addingactivated carbon and conductive agent, then, dispersing by using a highpressure dispersion machine, applying said electrode solution on aconductive foil in a specified thickness, and drying to prepare acurrent collector, winding said current collector on a separator, andsealing in a nonaqueous electrode solution together with lead-outelectrodes.
 8. An electric double layer capacitor comprising: (a) aconductor having planes; (b) a current collector installed at least onone of said planes of said conductor, said current collector including:(1) an activated carbon, (2) a conductive agent, and (3) a water-solublehigh polymer material and (4) at least one resin selected from the groupconsisting of fluoroplastic, latex resin, low softening point resin, andcrosslinking resin, and said conductor having said current collectorbeing at least one of a wound shape and a laminated shape through aseparator; (c) a nonaqueous electrode solution in which said conductorhaving said current collector is immersed; and (d) an electrodeconnected to said conductor.
 9. An electric double layer capacitor ofclaim 8, wherein said current collector has a density in a range fromabout 0.35 g/cc to about 1.50 g/cc.
 10. An electric double layercapacitor of claim 8, wherein said water-soluble high polymer materialincludes at least one material selected from the group consisting ofammonium salt of carboxy methyl cellulose resin, polyvinyl alcohol,methyl cellulose, and hydroxy propyl cellulose resin.
 11. An electricdouble layer capacitor of claim 8, wherein said current collector isinstalled on both sides of said conductor.
 12. An electric double layercapacitor of claim 8, wherein said conductive agent is at least oneselected from the group consisting of acetylene black, Ketienblack,graphite powder, metal powder, and conductive high polymer material. 13.An electric double layer capacitor of claim 8, wherein said one resin issaid latex resin, said latex resin is at least one selected from thegroup consisting of natural latex, styrene-butadiene rubber,nitrile-butadiene rubber, butadiene copolymer, styrene-butadienecopolymer, and carboxy denatured styrene-butadiene copolymer, and saidactivated carbon, said conductive agent, and said latex resin aredispersed in said water-soluble high polymer material.
 14. An electricdouble layer capacitor of claim 8, wherein said one resin is said lowsoftening point resin, and said low softening point resin has a glasstransition temperature of −10 deg. C. or less.
 15. An electric doublelayer capacitor of claim 8, wherein said one resin is said low softeningpoint resin, said low softening point resin is at least one selectedfrom the group consisting of vinyl chloride, ethylene-vinyl chloridecopolymer resin, vinylidene chloride latex, chlorinated resin, vinylacetate resin, polyvinyl butyral, polyvinyl formal, bisphenol systemepoxy resin, polyurethane resin, styrenebutadiene rubber, butadienerubber, isoprene rubber, nitrile-butadiene rubber, urethane rubber,silicone rubber and acrylic rubber, and said activated carbon, saidconductive agent, and said low softening point resin are dispersed insaid water-soluble high polymer material.
 16. An electric double layercapacitor of claim 8, wherein said at least one resin includes saidcrosslinking resin, wherein said crosslinking resin is chemicallycrosslinked.
 17. An electric double layer capacitor of claim 8, whereinsaid current collector has a thickness in a range from about 20 micronsto about 10 mm.
 18. An electric double layer capacitor of claim 8,wherein said conductor and said current collector installed on saidsurface of said conductor are wound in a winding diameter of about 5 mmor less.
 19. An electric double layer capacitor of claim 8, wherein saidconductor and said current collector installed on one of said planes ofsaid conductor have a plurality of current collectors, and each currentcollector of said plurality of current collectors is laminated throughsaid separator.
 20. An electric double layer capacitor having aplurality of the electric double layer capacitors of claim 8, whereinsaid each electric double layer capacitor is connected in series.
 21. Anelectric double layer capacitor having a plurality of the electricdouble layer capacitors of claim 8, wherein said each electric doublelayer capacitor is connected in parallel.
 22. An electric double layercapacitor of claim 8, wherein the total of said water-soluble highpolymer material and said one resin is in a range from about 1 part byweight to about 200 parts by weight, in 100 parts by weight of saidactivated carbon.
 23. An electric double layer capacitor comprising: (a)a conductor having planes; (b) a current collector installed at least onone of said planes of said conductor, said current collector including:(1) an activated carbon, (2) a conductive agent, and (3) a water-solublehigh polymer material and (4) at least one resin selected from the groupconsisting of fluoroplastic, latex resin, low softening point resin, andcrosslinking resin, and said conductor having said current collectorbeing at least one of a wound shape and a laminated shape through aseparator; (c) a nonaqueous electrode solution in which said conductorhaving said current collector is immersed; and (d) an electrodeconnected to said conductor, wherein said one resin is fluoroplastic,said fluoroplastic is polytetrafluoroethylene resin, and said activatedcarbon, said conductive agent and said polytetrafluoroethylene resin aredispersed in said water-soluble high polymer material.
 24. Amanufacturing method of electric double layer capacitor comprising thesteps of: (a) preparing an electrode solution by uniformly mixing amixture including activated carbon, water-soluble high polymer material,and at least one resin selected from the group consisting offluoroplastic, latex resin, low softening point resin, and crosslinkingresin; (b) applying said electrode solution on a conductor, and dryingto form a current collector; (c) forming at least one shape of windingshape and laminating shape said conductor having said current collectorthrough a separator; and (d) installing said conductor having saidcurrent collector in a nonaqueous electrode solution, wherein said oneresin is said fluoroplastic, and said fluoroplastic has particles with aparticle size of about 1 micron or less, being in an emulsion statedispersed in water.
 25. A manufacturing method of electric double layercapacitor comprising the steps of: (a) preparing an electrode solutionby uniformly mixing a mixture including activated carbon, water-solublehigh polymer material, and at least one resin selected from the groupconsisting of fluoroplastic, latex resin, low softening point resin, andcrosslinking resin; (b) applying said electrode solution on a conductor,and drying to form a current collector; (c) forming at least one shapeof winding shape and laminating shape said conductor having said currentcollector through a separator; and (d) installing said conductor havingsaid current collector in a nonaqueous electrode solution.
 26. Amanufacturing method of electric double layer capacitor of claim 25,wherein said water-soluble high polymer material is at least onematerial selected from the group consisting of ammonium salt of carboxymethyl cellulose resin, polyvinyl alcohol, methyl cellulose and hydroxypropyl cellulose resin.
 27. A manufacturing method of electric doublelayer capacitor of claim 25, wherein said one resin includes said latex,and said latex has particles with a particle size of about 1 micron orless, being in an emulsion state dispersed in water.
 28. A manufacturingmethod of electric double layer capacitor of claim 24 or 27, whereinsaid emulsion has a surface active agent, with the pH ranging from about4 to about 12, and at said step (a), said mixture is mixed whileapplying a pressure of 100 kg/cm² or more, so that said uniformlydispersed electrode solution is prepared.
 29. A manufacturing method ofelectric double layer capacitor of claim 25, wherein said one resinincludes said latex, and said latex has particles with a particle sizeof about 1 micron or less, being in an emulsion state dispersed in waternot containing at least one of ammonia and alcohol.
 30. A manufacturingmethod of electric double layer capacitor of claim 25, wherein saidelectrode solution has a viscosity in a range from about 1 poise toabout 200 poise, and at said step (b), said electrode solution isapplied on a first surface of said conductor at a thickness precisionfrom −10 microns to +10 microns at about 20 microns or more, then, in ahalf-dry state until said applied electrode solution is not driedcompletely, said conductor coated with said electrode solution is wound,then, said electrode solution is applied on a second surface of saidconductor at a thickness precision from −10 microns to +10 microns atabout 20 microns or more, then, said electrode solution applied on saidfirst surface and said second surface are dried simultaneously, andthen, said conductor having said electrode solution installed on saidfirst surface and said second surface is wound again.
 31. Amanufacturing method of electric double layer capacitor of claim 25,wherein at said step (a), said mixture is mixed while applying apressure of 100 kg/cm² or more, so that said uniformly dispersedelectrode solution is prepared.
 32. A manufacturing method of electricdouble layer capacitor of claim 25, wherein at said step (a), saidmixture is mixed by using a dispersion machine having at least onemixing unit made of at least one material selected from the groupconsisting of diamond, ceramic and cemented carbide, so that saiduniformly dispersed electrode solution is prepared.
 33. A manufacturingmethod of electric double layer capacitor of claim 25, wherein said oneresin is said fluoroplastic, said fluoroplastic has particles with aparticle size of about 1 micron or less, being in an emulsion statedispersed in water, and at said step (a), said mixture is mixed whileapplying a pressure of 100 kg/cm² or more, so that said uniformlydispersed electrode solution is prepared.
 34. A manufacturing method ofelectric double layer capacitor of claim 25, wherein said currentcollector has a density ranging from about 0.35 g/cc to about 1.50 g/cc.35. A manufacturing method of electric double layer capacitor of claim25, wherein the total of said water-soluble high polymer material andsaid one resin is in a range from about 1 part by weight to about 200parts by weight, in 100 parts by weight of said activated carbon.
 36. Amanufacturing method of electric double layer capacitor of claim 25,wherein at said step (a), said mixture is mixed, together with at leastone of purified water and ion exchange water, while applying a pressureof 100 kg/cm² or more, so that said uniformly dispersed electrodesolution is prepared.
 37. A manufacturing method of electric doublelayer capacitor of claim 25, wherein at said step (a), saidwater-soluble resin and at least one resin of said fluoroplastic andsaid latex are mixed, then, said activated carbon and said conductiveagent are added to prepare said mixed solution, then, said mixture ismixed while applying a pressure of 100 kg/cm² or more, so that saiduniformly dispersed electrode solution is prepared.
 38. A manufacturingmethod of electric double layer capacitor comprising the steps of: (a)preparing an electrode solution by uniformly mixing a mixture includingactivated carbon, water-soluble high polymer material, and at least oneresin selected from the group consisting of fluoroplastic, latex resin,low softening point resin, and crosslinking resin; (b) applying saidelectrode solution on a conductor, and drying to form a currentcollector; (c) forming at least one shape of winding shape andlaminating shape said conductor having said current collector through aseparator; and (d) installing said conductor having said currentcollector in a nonaqueous electrode solution, wherein said one resin issaid fluoroplastic, and said fluoroplastic has particles with a particlesize of about 1 micron or less, being in an emulsion state dispersed inwater, wherein said emulsion has a surface active agent, with pH rangingfrom about 4 to about
 12. 39. A manufacturing method of electric doublelayer capacitor comprising the steps of: (a) preparing an electrodesolution by uniformly mixing a mixture including activated carbon,water-soluble high polymer material, and at least one resin selectedfrom the group consisting of fluoroplastic, latex resin, low softeningpoint resin, and crosslinking resin; (b) applying said electrodesolution on a conductor and drying to form a current collector; (c)forming at least one shape of winding shape and laminating shape saidconductor having said current collector through a separator; (d)installing said conductor having said current collector in a nonaqueouselectrode solution, and processing said current collector by at leastone means of pressing and calendering to enhance at least one ofcharacteristics of density and surface smoothness.
 40. A manufacturingmethod of electric double layer capacitor comprising the steps of: (a)preparing an electrode solution by uniformly mixing a mixture includingactivated carbon, water-soluble high polymer material, and at least oneresin selected from the group consisting of fluoroplastic, latex resin,low softening point resin, and crosslinking resin; (b) applying saidelectrode solution on a conductor, and drying to form a currentcollector; (c) forming at least one shape of winding shape andlaminating shape said conductor having said current collector through aseparator; and (d) installing said conductor having said currentcollector in a nonaqueous electrode solution, wherein said one resinincludes said fluoroplastic, said fluoroplastic has particles with aparticle size of about 1 micron or less, being in an emulsion statedispersed in water, and said emulsion has the pH ranging from about 5 toabout
 12. 41. A manufacturing method of electric double layer capacitorcomprising the steps of: (a) preparing an electrode solution byuniformly mixing a mixture including activated carbon, water-solublehigh polymer material, and at least one resin selected from the groupconsisting of fluoroplastic, latex resin, low softening point resin, andcrosslinking resin; (b) applying said electrode solution on a conductor,and drying to form a current collector; (c) forming at least one shapeof winding shape and laminating shape said conductor having said currentcollector through a separator; and (d) installing said conductor havingsaid current collector in a nonaqueous electrode solution, wherein saidelectrode solution has a viscosity ranging from about 1 poise to about200 poise, and said electrode solution is applied as to form saidcurrent collector in a thickness of about 20 microns or more, atthickness precision ranging from −5 microns to +5 microns.
 42. Anelectric double layer capacitor comprising: (a) a conductor havingplanes; (b) a current collector installed at least on one of said planesof said conductor, said current collector including: (1) activatedcarbon, (2) conductive agent, and (3) at least one resin selected fromthe group consisting of water-soluble high polymer material,fluoroplastic, latex resin, low softening point resin, and crosslinkingresin, and said conductor having said current collector being at leastone of a wound shape and a laminated shape through a separator; (c) anonaqueous electrode solution in which said conductor having saidcurrent collector is immersed; and (d) an electrode connected to saidconductor, wherein said crosslinking resin contains at least onecatalyst of zirconia and zirconia compound, and said crosslinking resinis chemically crosslinked by the action of said catalyst.
 43. Amanufacturing method of electric double layer capacitor comprising thesteps of: (a) preparing an electrode solution by uniformly mixing amixture including activated carbon, water-soluble high polymer material,and at least one resin selected from the group consisting offluoroplastic, latex resin, low softening point resin, and crosslinkingresin; (b) applying said electrode solution on a conductor, and dryingto form a current collector; (c) forming at least one shape of windingshape and laminating shape said conductor having said current collectorthrough a separator; and (d) installing said conductor having saidcurrent collector in a nonaqueous electrode solution, wherein said oneresin includes said latex, and said latex has particles with a particlesize of about 1 micron or less, being in an emulsion state dispersed inwater, wherein said emulsion has a surface active agent, with pH rangingfrom about 4 to about
 12. 44. An electric double layer capacitorcomprising: (a) a conductor having planes; (b) a current collectorinstalled at least on one of said planes of said conductor, said currentcollector including: (1) activated carbon, (2) conductive agent, and (3)at least one resin selected from the group consisting of water-solublehigh polymer material, fluoroplastic, latex resin, low softening pointresin, and crosslinking resin, and said conductor having said currentcollector being at least one of a wound shape and a laminated shapethrough a separator; (c) a nonaqueous electrode solution in which saidconductor having said current collector is immersed; and (d) anelectrode connected to said conductor, wherein said current collectorhas a density in a range from about 0.35 g/cc to about 1.50 g/cc.
 45. Anelectric double layer capacitor of claim 42, 43 or 44, wherein saidwater-soluble high polymer material includes at least one materialselected from the group consisting of ammonium salt of carboxy methylcellulose resin, polyvinyl alcohol, methyl cellulose, and hydroxy propylcellulose resin.
 46. An electric double layer capacitor of claim 42, 43or 44, wherein said current collector is installed on both sides of saidconductor.
 47. An electric double layer capacitor of claim 42, 43 or 44,wherein said conductive agent is at least one selected from the groupconsisting of acetylene black, Ketienblack, graphite powder, metalpowder, and conductive high polymer material.
 48. An electric doublelayer capacitor of claim 42, 43 or 44, wherein said current collectorhas a thickness in a range from about 20 microns to about 10 mm.
 49. Anelectric double layer capacitor of claim 42, 43 or 44, wherein saidconductor and said current collector installed on said surface of saidconductor are wound in a winding diameter of about 5 mm or less.
 50. Anelectric double layer capacitor of claim 42, 43 or 44, wherein saidconductor and said current collector installed on said surface of saidconductor have a plurality of current collectors, and each currentcollector of said plurality of current collectors is laminated throughsaid separator.
 51. An electric double layer capacitor having aplurality of the electric double layer capacitors of claim 42, 43 or 44,wherein said each electric double layer capacitor is connected inseries.
 52. An electric double layer capacitor having a plurality of theelectric double layer capacitors of claim 42, 43 or 44, wherein saideach electric double layer capacitor is connected in parallel.
 53. Anelectric double layer capacitor comprising: (a) a conductor havingplanes; (b) a current collector installed at least on one of said planesof said conductor, said current collector including: (1) activatedcarbon, (2) conductive agent, and (3) at least one resin selected fromthe group consisting of water-soluble high polymer material,fluoroplastic, latex resin, low softening point resin, and crosslinkingresin, and said conductor having said current collector being at leastone of a wound shape and a laminated shape through a separator; (c) anonaqueous electrode solution in which said conductor having saidcurrent collector is immersed; and (d) an electrode connected to saidconductor, wherein said crosslinking resin is chemically crosslinked.